Vectors_params - This document briefly describes all Vectors
internal parameters.
Parameter descriptions follow, in alphabetical order. Each
description begins with a line giving the three-character mnemonic name of
the parameter, the phrase for which the mnemonic stands, the intrinsic type
of the parameter, and an indication of whether or not it is an array.
- ACM - Arrow Color Mode -
Integer
-
ACM controls how color is applied to filled vector arrows. It
applies only when AST has the value 1. Its behavior also depends on the
setting of the parameter CTV. Assuming that CTV is set to a non-zero
value, implying that multi-colored vectors are desired, ACM has the
following settings:
Value |
Effect |
----- |
------ |
-2 |
Multi-colored fill; outline off |
-1 |
Fill off; multi-colored outline |
0 |
Multi-colored fill; mono-colored outline |
1 |
Mono-colored fill; multi-colored outline |
2 |
Multi-colored fill; multi-colored outline |
Mono-colored outlines use the current GKS polyline color
index. Mono-colored fill uses the current GKS fill color index. When CTV
is set to 0, both the fill and the outlines become mono-colored, and
therefore only modes -2, -1, and 0 remain distinguishable. The default
value is 0.
- AFO - Arrow Fill Over Arrow
Lines - Integer
- If AFO is set to 1, the perimeter outline of a filled vector arrow is
drawn first, underneath the fill. In this case, you must set the line
thickness parameter (LWD) to a value greater than unity in order for the
line to appear completely. The advantage of drawing the line underneath is
that the full extent of the fill appears, resulting in a crisper, more
sharply defined arrow; when the line is drawn on top of the fill using a
different color index, the fill color may be partially or completely
obscured, especially for small vector arrows. AFO has an effect only when
the parameter AST is set to 1. The default value of AFO is 1.
- AIR - Arrow Interior Reference
Fraction - Real
- AIR specifies the distance from the point of the arrowhead of a filled
vector arrow drawn at the reference length to the point where the
arrowhead joins with the line extending to the tail of the arrow. Its
value represents a fraction of the reference length. This distance is
adjusted proportionally to the X component of the arrowhead size for
vector arrows whose length differs from the reference length. See VRL for
an explanation of how the reference length is determined. AIR has an
effect only when AST is set to 1. AIR is allowed to vary between 0.0 and
1.0 and its default value is 0.33.
- AMN - Arrow Head Minimum Size -
Real
- Specifies a minimum length for the two lines representing the point of the
vector arrow head, as a fraction of the viewport width. AMN has an effect
only for line-drawn vector arrows (parameter AST set to 0). Normally the
arrow head size is scaled proportionally to the length of the vector. This
parameter allows you to ensure that the arrow head will remain
recognizable even for very short vectors. Note that you can cause all the
arrowheads in the plot to be drawn at the same size if you set AMN and AMX
to the same value. If you set both AMN and AMX to 0.0 the arrowheads will
not be drawn at all. The default value is 0.005.
- AMX - Arrow Head Maximum Size -
Real
- Specifies a maximum length for the two lines representing the point of the
vector arrow head, as a fraction of the viewport width. AMX has an effect
only for line-drawn vector arrows (parameter AST set to 0). Normally the
arrow head is scaled proportionally to the length of the vector. This
parameter allows you to ensure that the arrow heads do not become
excessively large for high magnitude vectors. Note that you can cause all
the arrowheads in the plot to be drawn at the same size if you set AMN and
AMX to the same value. If you set both AMN and AMX to 0.0 the arrowheads
will not be drawn at all. The default value is 0.05.
- AST - Arrow Style -
Integer
-
If AST is set to 0, the vector arrows are drawn using lines
only. When AST is set to 1, the vectors are plotted using variable width
filled arrows, with an optional outline. If AST is set to 2, wind barb
glyphs are used to represent the vectors.There are parameters for
controlling the appearance of each style. These have an effect only for
one value of AST. However, certain parameters apply to all arrow styles.
Here is a table of parameters that affect the appearance of vectors and
how their behavior is affected by the setting of AST:
Parameter |
Line-Drawn Arrows |
Filled Arrows |
Wind Barbs |
--------- |
----------------- |
------------- |
---------- |
ACM |
|
x |
|
AFO |
|
x |
|
AIR |
|
x |
|
AMN |
x |
|
|
AMX |
x |
|
|
AWF |
|
x |
|
AWR |
|
x |
|
AXF |
|
x |
|
AXR |
|
x |
|
AYF |
|
x |
|
AYR |
|
x |
|
CLR |
x |
x |
x |
CTV |
x |
x |
x |
LWD |
x |
x |
x |
NLV |
x |
x |
x |
PAI |
x |
x |
x |
TVL |
x |
x |
x |
WBA |
|
|
x |
WBC |
|
|
x |
WBD |
|
|
x |
WBS |
|
|
x |
WBT |
|
|
x |
When filled arrows are used, colors associated with the
threshold levels may be applied to either or both the fill or the
outline of the arrow. When fill is drawn over the outline (AFO set to
1), LWD should be set to a value greater than 1.0 in order for the
outline to be fully visible. The default value of AST is 0.
- AWF - Arrow Width Fractional
Minimum - Real
- AWF specifies the width of a filled arrow drawn at the minimum length, as
a fraction of the width of an arrow drawn at the reference length. If AWF
has the value 0.0, then the ratio of the arrow width to the arrow length
will be constant for all arrows in the plot. If given the value 1.0, the
width will itself be constant for all arrows in the plot, regardless of
length. See VFR for a discussion of how the minimum length is determined.
AWF has an effect only when AST is set to 1. AWF is allowed to vary
between 0.0 and 1.0 and its default value is 0.0.
- AWR - Arrow Width Reference
Fraction - Real
- AWR specifies the width of a filled vector arrow drawn at the reference
length, as a fraction of the reference length. See VRL for an explanation
of how the reference length is determined. AWR has an effect only when AST
is set to 1. AWR is allowed to vary between 0.0 and 1.0 and its default
value is 0.03.
- AXF - Arrow X-Coord Fractional
Minimum - Real
- AXF specifies the X component of the head of a filled vector arrow drawn
at the minimum length, as a fraction of the X component of the head of an
arrow drawn at the reference length. The X component of the arrowhead is
the distance from the point of the arrowhead to a point along the
centerline of the arrow perpendicular the arrowhead´s rear tips. If
AXF has the value 0.0, then the ratio of the X component of the arrowhead
size to the arrow length will be constant for all vectors in the plot. If
given the value 1.0, the arrowhead X component will itself be constant for
all arrows in the plot, regardless of their length. See VRL for an
explanation of how the reference length is determined. AXF has an effect
only when AST is set to 1. AXF is allowed to vary between 0.0 and 1.0 and
its default value is 0.0.
- AXR - Arrow X-Coord Reference
Fraction - Real
- AXR specifies the X component of the head of a filled vector arrow drawn
at the reference length, as a fraction of reference length. The X
component of the arrowhead is the distance from the point of the arrowhead
to a point along the centerline of the arrow perpendicular the
arrowhead´s rear tips. See VRL for an explanation of how the
reference length is determined. AXR has an effect only when AST is set to
1. AXR is allowed to vary between 0.0 and 2.0 and its default value is
0.36.
- AYF - Arrow Y-Coord Fractional
Minimum - Real
- The value of this parameter, when added to the minimum width value,
specifies the Y component length of the arrowhead size for a filled arrow
drawn at the minimum length, as a fraction of the length specified by AYF.
If given the value 1.0, the arrowhead Y component will extend the same
distance perpendicularly from the edge of all arrows in the plot,
regardless of their length and width. This can be a useful resource to
adjust to ensure that the points of even very short vector arrows remain
visible. See VFR for a discussion of how the minimum length is determined.
AYF has an effect only when AST is set to 1. AYF is allowed to vary
between 0.0 and 1.0 and its default value is 0.25.
- AYR - Arrow Y-Coord Reference
Fraction - Real
- AYR specifies the perpendicular distance from one side of a filled vector
arrowdrawn at the reference length to one of the back tips of the
arrowhead. The value represents a fraction of the value of of the
reference length and, when added to half the arrow width, determines the Y
component of the arrowhead size. See VRL for an explanation of how the
reference length is determined. AYR has an effect only when AST is set to
1. AYR is allowed to vary between 0.0 and 1.0 and its default value is
0.12.
- CLR - Array of GKS Color Indices
- Integer Array
- This parameter represents an array containing the GKS color index to use
for coloring the vector when the scalar quantity is less than or equal to
the threshold value with the same index in the TVL threshold value array.
Depending on the settings of AST and ACM it may specify a set of fill
color indexes, a set of line color indexes, or both. In order to access a
particular element of the CLR array, you must first set the value of PAI,
the parameter array index parameter, to the value of the array
element´s index. All elements of the array are set to one
initially. Note that the Vectors utility makes no calls to set the GKS
color representation (GSCR), nor ever modifies the contents of the CLR
array; therefore you are responsible for creating a suitably graduated
color palette and assigning the color index values into the CLR array,
prior to calling VVECTR. Typically, assuming the desired RGB values have
been previously stored in a 2 dimensional 3 x n array called RGB, you loop
through the calls that set up the color representation and color index as
in the following example for a fourteen color palette:
DO 100 I=1,14,1
CALL GSCR (1,I,RGB(1,I),RGB(2,I),RGB(3,I))
CALL VVSETI(´PAI -- Parameter Array Index´, I)
CALL VVSETI(´CLR -- GKS Color Index´, I)
100 CONTINUE
-
- See the descriptions of CTV, NLV, and TVL for details on configuring the
vector coloring scheme.
- CPM - Compatibility Mode -
Integer
- Controls the degree of compatibility between pre-Version 3.2 capabilities
of the Vectors utility and later versions. You can independently control
three behaviors using the nine settings provided:
- use of VELVCT and VELVEC input parameters
- use of variables initialized in the VELDAT block data statement
- use of the old mapping routines, FX, FY, MXF, and MYF.
-
- Note, however, that when using the Version 3.2 entry points VVINIT and
VVECTR, only the third behavior option has any meaning.
When CPM is set to 0, its default value, the Vectors
utility´s behavior varies depending on whether you access it
through one of the pre-Version 3.2 entry points (VELVCT, VELVEC, and
EZVEC), or through the VVINIT/VVECTR interface. Otherwise, positive
values result in invocation of the pre-Version 3.2 mapping routines (FX,
FY, MXF, and MYF) for the conversion from data to user coordinates.
Negative values cause VVMPXY or perhaps VVUMXY to be used instead. When
using the pre-Version 3.2 interface, odd values of CPM cause the data
values in the VELDAT block data subroutine to override corresponding
values initialized in the Version 3.2 VVDATA block data subroutine, or
set by the user calling VVSETx routines. Values of CPM with absolute
value greater than two cause some of the input arguments to VELVEC and
VELVCT to be ignored. These include FLO, HI, NSET, ISPV, SPV and (for
VELVCT only) LENGTH.
Here is a table of the nine settings of CPM and their effect
on the operation of the Vectors utility:
Value |
Use FX, FY, etc. |
Use VELDAT data |
Use input args |
----- |
---------------- |
--------------- |
-------------- |
-4 |
no |
no |
no |
-3 |
no |
yes |
no |
-2 |
no |
no |
yes |
-1 |
no |
yes |
yes |
0 |
old - yes; new - no (*) |
yes |
yes |
1 |
yes |
yes |
yes |
2 |
yes |
no |
yes |
3 |
yes |
yes |
no |
4 |
yes |
no |
no |
(*) Old means EZVEC, VELVEC, VELVCT entry point; new,
VVINIT/VVECTR. Only the first column applies to the VVINIT/VVECTR
interface. See the velvct man page for more detailed emulation
information.
- CTV - Color Threshold Value
Control - Integer
- In conjunction with NLV, this parameter controls vector coloring and the
setting of threshold values. The vectors may be colored based on on the
vector magnitude or on the contents of a scalar array (VVINIT/VVECTR input
argument, P). A table of supported options follows:
- Value
- Action
- -2
- Color vector arrows based on scalar array data values; the user is
responsible for setting up threshold level array, TVL
- -1
- Color vector arrows based on vector magnitude; the user is responsible for
setting up values of threshold level array.
- 0(default)
- Color all vectors according to the current GKS polyline color index value.
Threshold level array, TVL and GKS color index array, CLR are not
used.
- 1
- Color vector arrows based on vector magnitude; VVINIT assigns values to
the first NLV elements of the threshold level array, TVL.
- 2
- Color vector arrows based on scalar array data values; VVINIT assigns
values to the first NLV elements of the threshold level array, TVL.
-
- If you make CTV positive, you must initialize Vectors with a call to
VVINIT after the modification.
- DMN - NDC Minimum Vector Size -
Real, Read-Only
- This parameter is read-only and has a useful value only following a call
to VVECTR (directly or through the compatibility version of VELVCT). You
may retrieve it in order to determine the length in NDC space of the
smallest vector actually drawn (in other words, the smallest vector within
the boundary of the user coordinate space that is greater than or equal in
magnitude to the value of the VLC parameter). It is initially set to a
value of 0.0.
- DMX - NDC Maximum Vector Size -
Real, Read-Only
- Unlike DMN this read-only parameter has a potentially useful value
betweens calls to VVINIT and VVECTR. However, the value it reports may be
different before and after the call to VVECTR. Before the VVECTR call it
contains the length in NDC space that would be used to render the maximum
size vector assuming the user-settable parameter, VRL is set to its
default value of 0.0. After the VVECTR call it contains the NDC length
used to render the largest vector actually drawn (in other words, the
largest vector within the boundary of the user coordinate space that is
less than or equal in magnitude to the value of the VHC parameter). See
the section on the VRL parameter for information on using the value of DMX
after the VVINIT call in order to adjust proportionally the lengths of all
the vectors in the plot. It is initially set to a value of 0.0.
- DPF - Vector Label Decimal Point
Control Flag - Integer
- If DPF is set to a non-zero value, and the optional vector magnitude
labels are enabled, the magnitude values are scaled to fit in the range 1
to 999. The labels will contain 1 to 3 digits and no decimal point.
Otherwise, the labels will consist of a number up to six characters long,
including a decimal point. By default DPF is set to the value 1.
- LBC - Vector Label Color -
Integer
- This parameter specifies the color to use for the optional vector
magnitude labels, as follows:
- Value
- Action
- < -1
- Draw labels using the current GKS text color index
- -1 (default)
- Draw labels using the same color as the corresponding vector arrow
- >=0
- Draw labels using the LBC value as the GKS text color index
- LBL - Vector Label Flag -
Integer
- If set non-zero, Vectors draws labels representing the vector magnitude
next to each arrow in the field plot. The vector labels are primarily
intended as a debugging aid, since in order to avoid excessive overlap,
you must typically set the label text size too small to be readable
without magnification. For this reason, as well as for efficiency, unlike
the other graphical text elements supported by the Vectors utility, the
vector labels are rendered using low quality text.
- LBS - Vector Label Character
Size - Real
- This parameter specifies the size of the characters used for the vector
magnitude labels as a fraction of the viewport width. The default value is
0.007.
- LWD - Vector Linewidth -
Real
-
LWD controls the linewidth used to draw the lines that form
vector arrows and wind barbs. When the arrows are filled (AST is set to
1) LWD controls the width of the arrow's outline. If the fill is drawn
over the outline (AFO set to 1) then LWD must be set to a value greater
than 1.0 in order for the outline to appear properly. When AST has the
value 2, LWD controls the width of the line elements of wind barbs. When
AST is set to 0, specifying line-drawn vector arrows, the linewidth
applies equally to the body of the vector and the arrowhead. Overly
thick lines may cause the arrow heads to appear smudged. This was part
of the motivation for developing the option of filled vector arrows.
Note that since linewidth in NCAR Graphics is always calculated relative
to a unit linewidth that is dependent on the output device, you may need
to adjust the linewidth value depending on the intended output device to
obtain a pleasing plot. The default is 1.0, specifying a
device-dependent minimum linewidth.
- MAP - Map Transformation Code -
Integer
- MAP defines the transformation between the data and user coordinate space.
Three MAP parameter codes are reserved for pre-defined transformations, as
follows:
- Value
- Mapping transformation
- 0 (default)
- Identity transformation between data and user coordinates: array indices
of U, V, and P are linearly related to data coordinates.
- 1
- Ezmap transformation: first dimension indices of U, V, and P are linearly
related to longitude; second dimension indices are linearly related to
latitude.
- 2
- Polar to rectangular transformation: first dimension indices of U, V, and
P are linearly related to the radius; second dimension indices are
linearly related to the angle in degrees.
-
- If MAP has any other value, Vectors invokes the user-modifiable
subroutine, VVUMXY, to perform the mapping. The default version of VVUMXY
simply performs an identity transformation. Note that, while the Vectors
utility does not actually prohibit the practice, the user is advised not
to use negative integers for user-defined mappings, since other utilities
in the NCAR Graphics toolkit attach a special meaning to negative mapping
codes.
For all the predefined mappings, the linear relationship
between the grid array indices and the data coordinate system is
established using the four parameters, XC1, XCM, YC1, and YCN. The X
parameters define a mapping for the first and last indices of the first
dimension of the data arrays, and the Y parameters do the same for the
second dimension. If MAP is set to a value of one, be careful to ensure
that the SET parameter is given a value of zero, since the Ezmap
routines require a specific user coordinate space for each projection
type, and internally call the SET routine to define the user to NDC
mapping. Otherwise, you may choose whether or not to issue a SET call
prior to calling VVINIT, modifying the value of SET as required. See the
description of the parameter, TRT, and the vvumxy man page for more
information.
- MNC - Minimum Vector Text Block
Color - Integer
- MNC specifies the color of the minimum vector graphical text output block
as follows:
- Value
- Action
- <-2
- Both the vector arrow and the text are colored using the current text
color index.
- -2
- If the vectors are colored by magnitude, both the vector arrow and the
text use the GKS color index associated with the minimum vector magnitude.
Otherwise, the vector arrow uses the current polyline color index and the
text uses the current text color index.
- -1 (default)
- If the vectors are colored by magnitude, the vector arrow uses the GKS
color index associated with the minimum vector magnitude. Otherwise the
vector arrow uses the current polyline color index. The text is colored
using the current text color index in either case.
- >= 0
- The value of MNC is used as the color index for both the text and the
vector arrow
-
- See the description of MNT for more information about the minimum vector
text block.
- MNP - Minimum Vector Text Block
Positioning Mode - Integer
- This parameter allows you to justify the minimum vector text block, taken
as a single unit, relative to the text block position established by the
parameters, MNX and MNY. Nine positioning modes are available, as
follows:
- Mode
- Justification
- -4
- The lower left corner of the text block is positioned at MNX, MNY.
- -3
- The center of the bottom edge is positioned at MNX, MNY.
- -2
- The lower right corner is positioned at MNX, MNY.
- -1
- The center of the left edge is positioned at MNX, MNY.
- 0
- The text block is centered along both axes at MNX, MNY.
- 1
- The center of the right edge is positioned at MNX, MNY.
- 2
- The top left corner is positioned at MNX, MNY.
- 3
- The center of the top edge is positioned at MNX, MNY.
- 4 (default)
- The top right corner is positioned at MNX, MNY.
-
- See the description of MNT for more information about the minimum vector
text block.
- MNS - Minimum Vector Text Block
Character Size - Real
- MNS specifies the size of the characters used in the minimum vector
graphics text block as a fraction of the viewport width. See the
description of MNT for more information about the minimum vector text
block. The default value of MNS is 0.0075.
- MNT - Minimum Vector Text String
- Character* 36
- The minimum vector graphics text block consists of a user-definable text
string centered underneath a horizontal arrow. If the parameter VLC is set
negative the arrow is rendered at the size of the reference minimum
magnitude vector (which may be smaller than any vector that actually
appears in the plot). Otherwise, the arrow is the size of the smallest
vector in the plot. Directly above the arrow is a numeric string in
exponential format that represents the vector's magnitude.
Use MNT to modify the text appearing below the vector in the
minimum vector graphics text block. Currently the string length is
limited to 36 characters. Set MNT to a single space (´ ´)
to remove the text block, including the vector arrow and the numeric
magnitude string, from the plot. The default value is ´Minimum
Vector´
- MNX - Minimum Vector Text Block
X Coordinate - Real
- MNX establishes the X coordinate of the minimum vector graphics text block
as a fraction of the viewport width. Values less than 0.0 or greater than
1.0 are permissible and respectively represent regions to the left or
right of the viewport. The actual position of the block relative to MNX
depends on the value assigned to MNP. See the descriptions of MNT and MNP
for more information about the minimum vector text block. The default
value of MNX is 0.475.
- MNY - Minimum Vector Text Block
Y Coordinate - Real
- MNY establishes the Y coordinate of the minimum vector graphics text block
as a fraction of the viewport height. Values less than 0.0 or greater than
1.0 are permissible and respectively represent regions below or above the
viewport. The actual position of the block relative to MNY depends on the
value assigned to MNP. See the descriptions of MNT and MNP for more
information about the minimum vector text block. The default value of MNY
is -0.01.
- MSK - Mask To Area Map Flag -
Integer
- Use this parameter to control masking of vectors to an existing area map
created by routines in the Areas utility. When MSK is greater than 0,
masking is enabled and an the area map must be set up prior to the call to
VVECTR. The area map array and, in addition, the name of a user-definable
masked drawing routine, must be passed as input parameters to VVECTR.
Various values of the MSK parameter have the following effects:
- Value
- Effect
- <= 0 (default)
- No masking of vectors.
- 1
- The subroutine ARDRLN is called internally to decompose the vectors into
segments contained entirely within a single area. ARDRLN calls the
user-definable masked drawing subroutine.
- >1
- Low precision masking. ARGTAI is called internally to get the area
identifiers for the vector base position point. Then the user-definable
masked drawing subroutine is called to draw the vector. Vectors with
nearby base points may encroach into the intended mask area.
-
- See the man page vvudmv for further explanation of masked drawing of
vectors
- MXC - Maximum Vector Text Block
Color - Integer
- MXC specifies the color of the maximum vector graphical text output block
as follows:
- Value
- Action
- <-2
- Both the vector arrow and the text are colored using the current text
color index.
- -2
- If the vectors are colored by magnitude, both the vector arrow and the
text use the GKS color index associated with the minimum vector magnitude.
Otherwise, the vector arrow uses the current polyline color index and the
text uses the current text color index.
- -1 (default)
- If the vectors are colored by magnitude, the vector arrow uses the GKS
color index associated with the minimum vector magnitude. Otherwise the
vector arrow uses the current polyline color index. The text is colored
using the current text color index in either case.
- >= 0
- The value of MXC is used as the color index for both the text and the
vector arrow
-
- See the description of MXT for more information about the maximum vector
text block.
- MXP - Maximum Vector Text Block
Positioning Mode - Integer
- This parameter allows you to justify the maximum vector text block, taken
as a single unit, relative to the text block position established by the
parameters, MXX and MXY. Nine positioning modes are available, as
follows:
- Mode
- Justification
- -4
- The lower left corner of the text block is positioned at MXX, MXY.
- -3
- The center of the bottom edge is positioned at MXX, MXY.
- -2
- The lower right corner is positioned at MXX, MXY.
- -1
- The center of the left edge is positioned at MXX, MXY.
- 0
- The text block is centered along both axes at MXX, MXY.
- 1
- The center of the right edge is positioned at MXX, MXY.
- 2
- The top left corner is positioned at MXX, MXY.
- 3
- The center of the top edge is positioned at MXX, MXY.
- 4
- The top right corner is positioned at MXX, MXY.
-
- See the description of MXT for more information about the maximum vector
text block.
- MXS - Maximum Vector Text Block
Character Size - Real
- MXS specifies the size of the characters used in the maximum vector
graphics text block as a fraction of the viewport width. See the
description of MXT for more information about the maximum vector text
block. The default value is 0.0075.
- MXT - Maximum Vector Text String
- Character* 36
- The maximum vector graphics text block consists of a user-definable text
string centered underneath a horizontal arrow. If the parameter VHC is set
negative the arrow is rendered at the size of the reference maximum
magnitude vector (which may be larger than any vector that actually
appears in the plot). Otherwise, the arrow is the size of the largest
vector in the plot. Directly above the arrow is a numeric string in
exponential format that represents the magnitude of this vector.
Use MXT to modify the text appearing below the vector in the
maximum vector graphics text block. Currently the string length is
limited to 36 characters. Set MXT to a single space (´ ´)
to completely remove the text block, including the vector arrow and the
numeric magnitude string, from the plot. Note that the name
"Maximum Vector Text Block" is no longer accurate, since using
the parameter VRM it is now possible to establish a reference magnitude
that is smaller than the maximum magnitude in the data set. A more
accurate name would be "Reference Vector Text Block". The
default value of MXT is ´Maximum Vector´.
- MXX - Maximum Vector Text Block
X Coordinate - Real
- MXX establishes the X coordinate of the maximum vector graphics text block
as a fraction of the viewport width. Values less than 0.0 or greater than
1.0 are permissible and respectively represent regions below or above of
the viewport. The actual position of the block relative to MXX depends on
the value assigned to MXP. See the descriptions of MXT and MXP for more
information about the maximum vector text block. The default value is
0.525.
- MXY - Maximum Vector Text Block
Y Coordinate - Real
- MXY establishes the Y coordinate of the maximum vector graphics text block
as a fraction of the viewport width. Values less than 0.0 or greater than
1.0 are permissible and respectively represent regions below or above the
viewport. The actual position of the block relative to MXY depends on the
value assigned to MXP. See the descriptions of MXT and MXP for more
information about the maximum vector text block. The default value is
-0.01.
- NLV - Number of Colors Levels -
Integer
- NLV specifies the number of color levels to use when coloring the vectors
according to data in a scalar array or by vector magnitude. Anytime CTV
has a non-zero value, you must set up the first NLV elements of the color
index array CLR. Give each element the value of a GKS color index that
must be defined by a call to the the GKS subroutine, GSCR, prior to
calling VVECTR. If CTV is less than 0, in addition to setting up the CLR
array, you are also responsible for setting the first NLV elements of the
threshold values array, TVL to appropriate values. NLV is constrained to a
maximum value of 255. The default value of NLV is 0, specifying that
vectors are colored according to the value of the GKS polyline color index
currently in effect, regardless of the value of CTV. If CTV is greater
than 0, you must initialize Vectors with a call to VVINIT after modifying
this parameter.
- PAI - Parameter Array Index -
Integer
- The value of PAI must be set before calling VVGETC, VVGETI, VVGETR,
VVSETC, VVSETI, or VVSETR to access any parameter which is an array; it
acts as a subscript to identify the intended array element. For example,
to set the 10th color threshold array element to 7, use code like this:
CALL VVSETI (´PAI - PARAMETER ARRAY INDEX´,10)
CALL VVSETI (´CLR - Color Index´,7)
-
- The default value of PAI is one.
- PLR - Polar Input Mode -
Integer
- When PLR is greater than zero, the vector component arrays are considered
to contain the field data in polar coordinate form: the U array is treated
as containing the vector magnitude and the V array as containing the
vector angle. Be careful not to confuse the PLR parameter with the MAP
parameter set to polar coordinate mode (2). The MAP parameter relates to
the location of the vector, not its value. Here is a table of values for
PLR:
- Value
- Meaning
- 0 (default)
- U and V arrays contain data in cartesian component form.
- 1
- U array contains vector magnitudes; V array contains vector angles in
degrees.
- 2
- U array contain vector magnitudes; V array contains vector angles in
radians.
-
- You must initialize Vectors with a call to VVINIT after modifying this
parameter.
- PMN - Minimum Scalar Array Value
- Real, Read-Only
- You may retrieve the value specified by PMN at any time after a call to
VVINIT. It will contain a copy of the minimum value encountered in the
scalar data array. If no scalar data array has been passed into VVINIT it
will have a value of 0.0.
- PMX - Maximum Scalar Array Value
- Real
- You may retrieve the value specified by PMX at any time after a call to
VVINIT. It contains a copy of the maximum value encountered in the scalar
data array. If no scalar data array has been passed into VVINIT it will
have a value of 0.0.
- PSV - P Array Special Value -
Real
- Use PSV to indicate the special value that flags an unknown data value in
the P scalar data array. This value will not be considered in the
determination of the data set maximum and minimum values. Also, depending
on the setting of the SPC parameter, the vector may be specially colored
to flag the unknown data point, or even eliminated from the plot. You must
initialize Vectors with a call to VVINIT after modifying this
parameter.
- SET - SET Call Flag -
Integer
- Give SET the value 0 to inhibit the SET call VVINIT performs by default.
Arguments 5-8 of a SET call made by the user must be consistent with the
ranges of the user coordinates expected by Vectors. This is determined by
the mapping from grid to data coordinates as specified by the values of
the parameters XC1, XCM, YC1, YCN, and also by the mapping from data to
user coordinates established by the MAP parameter. You must initialize
Vectors with a call to VVINIT after modifying this parameter. The default
value of SET is 1.
- SPC - Special Color -
Integer
- SPC controls special value processing for the optional scalar data array
used to color the vectors, as follows:
- Value
- Effect
- < 0 (default)
- The P scalar data array is not examined for special values.
- 0
- Vectors at P scalar array special value locations are not drawn.
- > 0
- Vectors at P scalar array special value locations are drawn using color
index SPC.
-
- You must initialize Vectors with a call to VVINIT after modifying this
parameter.
- SVF - Special Value Flag -
Integer
- The special value flag controls special value processing for the U and V
vector component data arrays. Special values may appear in either the U or
V array or in both of them. Five different options are available (although
the usefulness of some of the choices is debatable):
- Value
- Effect
- 0 (default)
- Neither the U nor the V array is examined for special values
- 1
- Vectors with special values in the U array are not drawn
- 2
- Vectors with special values in the V array are not drawn
- 3
- Vectors with special values in either the U or V array are not drawn
- 4
- Vectors with special values in both the U and V arrays are not drawn
-
- The U and V special values are defined by setting parameters USV and VSV.
You must initialize Vectors with a call to VVINIT after modifying this
parameter.
- TRT - Transformation Type -
Integer
- As currently implemented, TRT further qualifies the mapping transformation
specified by the MAP parameter, as follows:
- Value
- Effect
- -1
- Direction, magnitude, and location are all transformed. This option is not
currently supported by any of the pre-defined coordinate system
mappings.
- 0
- Only location is transformed
- 1 (default)
- Direction and location are transformed
-
- This parameter allows you to distinguish between a system that provides a
mapping of location only into an essentially cartesian space, and one in
which the space itself mapped. To understand the difference, using polar
coordinates as an example, imagine a set of wind speed monitoring units
located on a radial grid around some central point such as an airport
control tower. Each unit´s position is defined in terms of its
distance from the tower and its angular direction from due east. However,
the data collected by each monitoring unit is represented as conventional
eastward and northward wind components. Assuming the towers´s
location is at a moderate latitude, and the monitoring units are
reasonably ´local´, this is an example of mapping a radially
defined location into a nearly cartesian space (i.e. the eastward
components taken alone all point in a single direction on the plot,
outlining a series of parallel straight lines). One would set MAP to two
(for the polar transformation) and TRT to zero to model this data on a
plot generated by the Vectors utility.
On the other hand, picture a set of wind data, again given as
eastward and northward wind components, but this time the center of the
polar map is actually the south pole. In this case, the eastward
components do not point in a single direction; instead they outline a
series of circles around the pole. This is a space mapping
transformation: one would again set MAP to two, but TRT would be set to
one to transform both direction and location.
Changing the setting of this parameter affects the end results
only when a non-uniform non-linear mapping occurs at some point in the
transformation pipeline. For this discussion a uniform linear
transformation is defined as one which satisfies the following
equations:
x_out = x_offset + scale_constant * x_in
y_out = y_offset + scale_constant * y_in
-
- If scale_constant is not the same for both the X axis and the Y axis then
the mapping is non-uniform.
This option is currently implemented only for the pre-defined
MAP parameter codes, 0 and 2, the identity mapping and the polar
coordinate mapping. However, it operates on a different stage of the
transformation pipeline in each case. The polar mapping is non-linear
from data to user coordinates. The identity mapping, even though
necessarily linear over the data to user space mapping, can have a
non-uniform mapping from user to NDC space, depending on the values
given to the input parameters of the SET call. This will be the case
whenever the LL input parameter is other than one, or when LL equals
one, but the viewport and the user coordinate boundaries do not have the
same aspect ratio. Thus for a MAP value of 2, TRT affects the mapping
between data and user space, whereas for MAP set to 0, TRT influences
the mapping between user and NDC space.
- TVL - Array of Threshold Values
- Real Array
- TVL is an array of threshold values that is used to determine the
individual vector color, when CTV and NLV are both non-zero. For each
vector the TVL array is searched for the smallest value greater than or
equal to the scalar value associated with the vector. The array subscript
of this element is used as an index into the CLR array. Vectors uses the
GKS color index found at this element of the CLR array to set the color
for the vector. Note that Vectors assumes that the threshold values are
monotonically increasing.
When CTV is less than 0, you are responsible for assigning
values to the elements of TVL yourself. To do this, first set the PAI
parameter to the index of the threshold level element you want to
define, then call VVSETR to set TVL to the appropriate threshold value
for this element. Assuming the desired values have previously been
stored in a array named TVALS, you could assign the threshold values for
a fourteen level color palette using the following loop:
DO 100 I=1,14,1
CALL VVSETI(PAI -- Parameter Array Index, I)
CALL VVSETR(TVL -- Threshold Value, TVALS(I))
100 CONTINUE
-
- When CTV is greater than 0, Vectors assigns values into TVL itself. Each
succeeding element value is greater than the preceding value by the value
of the expression:
(maximum_data_value - minimum_data_value) / NLV
-
- where the data values are either from the scalar data array or are the
magnitudes of the vectors in the vector component arrays. The first value
is equal to the minimum value plus the expression; the final value
(indexed by the value of NLV) is equal to the maximum value. If Vectors
encounters a value greater than the maximum value in the TVL array while
processing the field data, it gives the affected vector the color
associated with the maximum TVL value.
- USV - U Array Special Value -
Real
- USV is the U vector component array special value. It is a value outside
the range of the normal data used to indicate that there is no valid data
for this grid location. When SVF is set to 1 or 3, Vectors will not draw a
vector whose U component has the special value. You must initialize
Vectors with a call to VVINIT after modifying this parameter. It has a
default value of 1.0 E12.
- VFR - Minimum Vector Fractional
Length - Real
- Use this parameter to adjust the realized size of the reference minimum
magnitude vector relative to the reference maximum magnitude vector in
order to improve the appearance or perhaps the information content of the
plot. Specify VFR as a value between 0.0 and 1.0, where 0.0 represents an
unmodified linear scaling of the realized vector length, in proportion to
magnitude, and 1.0 specifies that the smallest vector be represented at
1.0 times the length of the largest vector, resulting in all vectors,
regardless of magnitude, having the same length on the plot. A value of
0.5 means that the smallest magnitude vector appears half as long as the
largest magnitude vector; intermediate sizes are proportionally scaled to
lengths between these extremes. Where there is a wide variation in
magnitude within the vector field, you can use this parameter to increase
the size of the smallest vectors to a usefully visible level. Where the
variation is small, you can use the parameter to exaggerate the
differences that do exist. See also the descriptions of VRL, VLC, VHC, and
VRM. The default value is 0.0.
- VHC - Vector High Cutoff Value -
Real
- If the parameter VRM is set to a value greater than 0.0, it supercedes the
use of VHC to specify the reference magnitude. VRM allows greater
flexibility in that it can be used to specify an arbitrary reference
magnitude that need not be the maximum magnitude contained in the data
set. VHC can still be used to set a high cutoff value -- no vectors with
magnitude greater than the cutoff value will be displayed in the plot.
If VRM has its default value, 0.0, VHC specifies the reference
maximum magnitude represented by an arrow of length VRL (as a fraction
of the viewport width). The realized length of each individual vector in
the plot is based on its magnitude relative to the reference maximum
magnitude and, if VFR is non-zero, the reference minimum magnitude (as
specified by VLC). Note that the reference maximum magnitude may be
greater than the magnitude of any vector in the dataset. The effect of
this parameter varies depending on its value, as follows:
- Value
- Effect
- < 0.0
- The absolute value of VHC unconditionally determines the reference maximum
magnitude. Vectors in the dataset with magnitude greater than VHC are not
displayed.
- 0.0 (default)
- The vector with the greatest magnitude in the dataset determines the
reference maximum magnitude.
- > 0.0
- The minimum of VHC and the vector with the greatest magnitude in the data
set determines the reference maximum magnitude. Vectors in the dataset
with magnitude greater than VHC are not displayed.
-
- Typically, for direct comparison of the output of a series of plots, you
would set VHC to a negative number, the absolute value of which is greater
than any expected vector magnitude in the series. You can turn on Vectors
statistics reporting using the parameter VST in order to see if any
vectors in the datasets do exceed the maximum magnitude you have
specified. See also the descriptions of the parameters VRM, VRL, DMX, VLC,
and VFR.
- VLC - Vector Low Cutoff Value -
Real
- Use this parameter to prevent vectors smaller than the specified magnitude
from appearing in the output plot. VLC also specifies the reference
minimum magnitude that is rendered at the size specified by the product of
VRL and VFR (as a fraction of the viewport width), when VFR is greater
than 0.0. Note that the reference minimum magnitude may be smaller than
the magnitude of any vector in the dataset. The effect of this parameter
varies depending on its value, as follows:
- Value
- Effect
- < 0.0
- The absolute value of VLC unconditionally determines the reference minimum
magnitude. Vectors in the dataset with magnitude less than VLC do not
appear.
- 0.0 (default)
- The vector with the minimum magnitude in the dataset determines the
reference minimum magnitude.
- > 0.0
- The maximum of VLC and the vector with the least magnitude in the data set
determines the reference minimum magnitude. Vectors in the dataset with
magnitude less than VLC do not appear.
-
- The initialization subroutine, VVINIT, calculates the magnitude of all the
vectors in the vector field, and stores the maximum and minimum values.
You may access these values by retrieving the read-only parameters, VMX
and VMN. Thus it is possible to remove the small vectors without prior
knowledge of the data domain. The following code fragment illustrates how
the smallest 10% of the vectors could be removed:
CALL VVINIT(...
CALL VVGETR(´VMX - Vector Maximum Magnitude´, VMX)
CALL VVGETR(´VMN - Vector Minimum Magnitude´, VMN)
CALL VVSETR(´VLC - Vector Low Cutoff Value´,
+ VMN+0.1*(VMX-VMN))
CALL VVECTR(...
-
- On the other hand, when creating a series of plots that you would like to
compare directly and you are using VFR to set a minimum realized size for
the vectors, you can ensure that all vectors of a particular length
represent the same magnitude on all the plots by setting both VHC and VLC
to negative values. If you do not actually want to remove any vectors from
the plot, make VLC smaller in absolute value than any expected magnitude.
You can turn on Vectors statistics reporting using the parameter VST in
order to see if any vectors in the datasets are less the minimum magnitude
you have specified. See also the descriptions of parameters VFR, VRL, VHC,
DMN, and VRM.
- VMD - Vector Minimum Distance -
Real
- If VMD is set to a value greater than 0.0, it specifies, as a fraction of
the viewport width, a minimum distance between adjacent vectors arrows in
the plot. The distribution of vectors is analyzed and then vectors are
selectively removed in order to ensure that the remaining vectors are
separated by at least the specified distance. The thinning algorithm
requires that you supply Vectors with a work array twice the size of the
VVINIT arguments N and M multiplied together. Use of this capability adds
some processing time to the execution of Vectors. If VMD is set to a value
greater than 0.0 and no work array is provided, an error condition
results.
If the data grid is transformed in such a way that adjacent
grid cells become very close in NDC space, as for instance in many map
projections near the poles, you can use this parameter to reduce the
otherwise cluttered appearance of these regions of the plot. The default
value of VMD is 0.0.
- VMN - Minimum Vector Magnitude -
Real, Read-Only
- After a call to VVINIT, VMN contains the value of the minimum vector
magnitude in the U and V vector component arrays. Later, after VVECTR is
called, it is modified to contain the magnitude of the smallest vector
actually displayed in the plot. This is the vector with the smallest
magnitude greater than or equal to the value specified by VLC, the vector
low cutoff parameter, (0.0 if VLC has its default value) that falls within
the user coordinate window boundaries. The value contained in VMN is the
same as that reported as the 'Minimum plotted vector magnitude' when
Vectors statistics reporting is enabled. It may be larger than the
reference minimum magnitude reported by the minimum vector text block if
you specify the VLC parameter as a negative value. VMN is initially set to
a value of 0.0.
- VMX - Maximum Vector Magnitude -
Real, Read-Only
- After a call to VVINIT, VMX contains the value of the maximum vector
magnitude in the U and V vector component arrays. Later, after VVECTR is
called, it is modified to contain the magnitude of the largest vector
actually displayed in the plot. This is the vector with the largest
magnitude less than or equal to the value specified by VHC, the vector
high cutoff parameter, (the largest floating point value available on the
machine if VHC has its default value, 0.0) that falls within the user
coordinate window boundaries. The value contained in VMX is the same as
that reported as the 'Maximum plotted vector magnitude' when Vectors
statistics reporting is enabled. It may be smaller than the reference
maximum magnitude reported by the maximum vector text block if you specify
the VHC parameter as a negative value. VMX is initially set to a value of
0.0.
- VPB - Viewport Bottom -
Real
- The parameter VPB has an effect only when SET is non-zero, specifying that
Vectors should do the call to SET. It specifies a minimum boundary value
for the bottom edge of the viewport in NDC space, and is constrained to a
value between 0.0 and 1.0. It must be less than the value of the Viewport
Top parameter, VPT. The actual value of the viewport bottom edge used in
the plot may be greater than the value of VPB, depending on the setting of
the Viewport Shape parameter, VPS. You must initialize Vectors with a call
to VVINIT after modifying this parameter. The default value of VPB is
0.05.
- VPL - Viewport Left -
Real
- The parameter VPL has an effect only when SET is non-zero, specifying that
Vectors should do the call to SET. It specifies a minimum boundary value
for the left edge of the viewport in NDC space, and is constrained to a
value between 0.0 and 1.0. It must be less than the value of the Viewport
Right parameter, VPR. The actual value of the viewport left edge used in
the plot may be greater than the value of VPL, depending on the setting of
the Viewport Shape parameter, VPS. You must initialize Vectors with a call
to VVINIT after modifying this parameter. The default value of VPL is
0.05.
- VPO - Vector Positioning Mode -
Integer
- VPO specifies the position of the vector arrow in relation to the grid
point location of the vector component data. Three settings are available,
as follows:
- Value
- Effect
- <0
- The head of the vector arrow is placed at the grid point location
- 0 (default)
- The center of the vector arrow is placed at the grid point location
- >0
- The tail of the vector arrow is placed at the grid point location
- VPR - Viewport Right -
Real
- The parameter VPR has an effect only when SET is non-zero, specifying that
Vectors should do the call to SET. It specifies a maximum boundary value
for the right edge of the viewport in NDC space, and is constrained to a
value between 0.0 and 1.0. It must be greater than the value of the
Viewport Left parameter, VPL. The actual value of the viewport right edge
used in the plot may be less than the value of VPR, depending on the
setting of the Viewport Shape parameter, VPS. You must initialize Vectors
with a call to VVINIT after modifying this parameter. The default value of
VPR is 0.95.
- VPS - Viewport Shape -
Real
- The parameter VPS has an effect only when SET is non-zero, specifying that
Vectors should do the call to SET; it specifies the desired viewport
shape, as follows:
- Value
- Effect
- <0.0
- The absolute value of VPS specifies the shape to use for the viewport., as
the ratio of the viewport width to its height,
- 0.0
- The viewport completely fills the area defined by the boundaries
specifiers, VPL, VPR, VPB, VPT
- >0.0,<1.0 (0.25, default)
- Use R = (XCM-XC1)/(YCN-YC1) as the viewport shape if MIN(R, 1.0/R) is
greater than VPS. Otherwise determine the shape as when VPS is equal to
0.0.
- >= 1.0
- Use R = (XCM-XC1)/(YCN-YC1) as the viewport shape if MAX(R, 1.0/R) is less
than VPS. Otherwise make the viewport a square.
-
- The viewport, whatever its final shape, is centered in, and made as large
as possible in, the area specified by the parameters VPB, VPL, VPR, and
VPT. You must initialize Vectors with a call to VVINIT after modifying
this parameter. The default value of VPS is 25.
- VPT - Viewport Top -
Real
- The parameter VPT has an effect only when SET is non-zero, specifying that
Vectors should do the call to SET. It specifies a maximum boundary value
for the top edge of the viewport in NDC space, and is constrained to a
value between 0.0 and 1.0. It must be greater than the value of the
Viewport Bottom parameter, VPB. The actual value of the viewport top edge
used in the plot may be less than the value of VPT, depending on the
setting of the Viewport Shape parameter, VPS. You must initialize Vectors
with a call to VVINIT after modifying this parameter. The default value of
VPT is 0.95.
- VRL - Vector Reference Length -
Real
- Use this parameter to specify the realized length of the reference
magnitude vector as a fraction of the viewport width. Based on this value
a reference length in NDC units is established, from which the length of
all vectors in the plot is derived. The relationship between magnitude and
length also depends on the setting of the minimum vector magnitude
fraction parameter, VFR, but, given the default value of VFR (0.0), the
length of each vector is simply proportional to its relative magnitude.
Note that the arrow size parameters, AMN and AMX, allow independent
control over the minimum and maximum size of the vector arrowheads.
Given a reference length, Vectors calculates a maximum length
based on the ratio of the reference magnitude to the larger of the
maximum magnitude in the data set and the reference magnitude itself.
This length is accessible in units of NDC via the read-only parameter,
DMX. If VRL is set less than or equal to 0.0, VVINIT calculates a
default value for DMX, based on the size of a grid box assuming a linear
mapping from grid coordinates to NDC space. The value chosen is one half
the diagonal length of a grid box. By retrieving the value of DMX and
calling GETSET to retrieve the viewport boundaries after the call to
VVINIT, you can make relative adjustments to the vector length, as shown
by the following example, where the maximum vector length is set to 1.5
times its default value:
CALL VVINIT(...
CALL VVGETR(´DMX - NDC Maximum Vector Size´, DMX)
CALL GETSET(VL,VR,VB,VT,UL,UR,UB,UT,LL)
VRL = 1.5 * DMX / (VR - VL)
CALL VVSETR(´VRL - Vector Realized Length´, VRL)
CALL VVECTR(...
-
- When VVECTR sees that VRL is greater than 0.0, it will calculate a new
value for DMX. If VRL is never set, the initially calculated value of DMX
is used as the reference length. Do not rely on the internal parameters
used for setting the viewport, VPL, VPR, VPB and VPT to retrieve
information about viewport in lieu of using the GETSET call. These values
are ignored entirely if the SET parameter is zero, and even if used, the
viewport may be adjusted from the specified values depending on the
setting of the viewport shape parameter, VPS. See also the descriptions of
VFR, VRM, and VHC. The default value of VRL is 0.0.
- VRM - Vector Reference Magnitude
- Real
- The introduction of the parameter VRM means that it is now possible to
specify an arbitrary vector magnitude as the reference magnitude appearing
in the "Maximum Vector Text Block" annotation. The reference
magnitude no longer needs to be greater or equal to the largest magnitude
in the data set. When VRM has a value greater than 0.0, it specifies the
magnitude of the vector arrow drawn at the reference length. See VRL for
an explanation of how the reference length is determined. If VRM is less
than or equal to 0.0, the reference magnitude is determined by the value
of VHC, the vector high cutoff value. If, in turn, VHC is equal to 0.0 the
maximum magnitude in the vector field data set becomes the reference
magnitude. The default value of VRM is 0.0.
- VST - Vector Statistics Output
Flag - Integer
- If VST is set to one, VVECTR writes a summary of its operation to the
default logical output unit, including the number of vectors plotted,
number of vectors rejected, minimum and maximum vector magnitudes, and if
coloring the vectors according to data in the scalar array, the maximum
and minimum scalar array values encountered. Here is a sample of the
output:
VVECTR Statistics
Vectors plotted: 906
Vectors rejected by mapping routine: 0
Vectors under minimum magnitude: 121
Vectors over maximum magnitude: 0
Other zero length vectors: 0
Rejected special values: 62
Minimum plotted vector magnitude: 9.94109E-02
Maximum plotted vector magnitude: 1.96367
Minimum scalar value: -1.00000
Maximum scalar value: 1.00000
- VSV - V Array Special Value -
Real
- VSV is the V vector component array special value. It is a value outside
the range of the normal data used to indicate that there is no valid data
for this grid location. When SVF is set to 2 or 3, Vectors will not draw a
vector whose V component has the special value. You must initialize
Vectors with a call to VVINIT after modifying this parameter. It has a
default value of 1.0 E12.
- WBA - Wind Barb Angle -
Real
-
WBA sets the angle of the wind barb ticks in degrees as
measured clockwise from the vector direction. It also sets the angle
between the hypotenuse of the triangle defining the pennant polygon and
the vector direction. You can render southern hemisphere wind barbs,
which by convention, have their ticks and pennants on the other side of
the shaft, by setting WBA to a negative value. WBA has an effect only
when AST has the value 2.
- WBC - Wind Barb Calm Circle Size
- Real
-
WBC sets the diameter of the circle used to represent small
vector magnitudes (less than 2.5) as a fraction of the overall wind barb
length (the value of the VRL parameter). WBC has an effect only when AST
has the value 2.
- WBD - Wind Barb Distance Between
Ticks - Real
-
WBD sets the distance between adjacent wind barbs ticks along
the wind barb shaft as a fraction of the overall wind barb length (the
value of the VRL parameter). Half this distance is used as the spacing
between adjacent wind barb pennants. Note that there is nothing to to
prevent ticks and/or pennants from continuing off the end of the shaft
if a vector of high enough magnitude is encountered. You are responsible
for adjusting the parameters appropriately for the range of magnitudes
you need to handle. WBD has an effect only when AST has the value 2.
- WBS - Wind Barb Scale Factor -
Real
-
WBS specifies a factor by which magnitudes passed to the wind
barb drawing routines are to be scaled. It can be used to convert vector
data given in other units into the conventional units used with wind
barbs, which is knots. For instance, if the data are in meters per
second, you could set WBS to 1.8974 to create a plot with conventional
knot-based wind barbs. Note that setting WBS does not currently have any
effect on the magnitude values written into the maximum or minimum
vector legends. WBS has an effect only when AST has the value 2.
- WBT - Wind Barb Tick Size -
Real
-
WBT the length of the wind barb ticks as a fraction of the
overall length of a wind barb (the value of the VRL parameter). The wind
barb length is defined as the length of the wind barb shaft plus the
projection of a full wind barb tick along the axis of the shaft.
Therefore, increasing the value of WBT, for a given value of VRL has the
effect of reducing the length of the shaft itself somewhat. You may need
to increase VRL itself to compensate. WBT also sets the hypotenuse
length of the triangle defining the pennant polygon. WBT has an effect
only when AST has the value 2.
- WDB - Window Bottom -
Real
- When VVINIT does the call to SET, the parameter WDB is used to determine
argument number 7, the user Y coordinate at the bottom of the window. If
WDB is not equal to WDT, WDB is used. If WDB is equal to WDT, but YC1 is
not equal to YCN, then YC1 is used. Otherwise, the value 1.0 is used. You
must initialize Vectors with a call to VVINIT after modifying this
parameter. The default value of WDB is 0.0.
- WDL - Window Left -
Real
- When VVINIT the call to SET, the parameter WDL is used to determine
argument number 5, the user X coordinate at the left edge of the window.
If WDL is not equal to WDR, WDL is used. If WDL is equal to WDR, but XC1
is not equal to XCM, then XC1 is used. Otherwise, the value 1.0 is used.
You must initialize Vectors with a call to VVINIT after modifying this
parameter. The default value of WDL is 0.0.
- WDR - Window Right -
Real
- When VVINIT does the call to SET, the parameter WDR is used to determine
argument number 6, the user X coordinate at the right edge of the window.
If WDR is not equal to WDL, WDR is used. If WDR is equal to WDL, but XCM
is not equal to XC1, then XCM is used. Otherwise, the value of the VVINIT
input parameter, M, converted to a real, is used. You must initialize
Vectors with a call to VVINIT after modifying this parameter. The default
value of WDR is 0.0.
- WDT - Window Top - Real
- When VVINIT does the call to SET, the parameter WDB is used to determine
argument number 8, the user Y coordinate at the top of the window. If WDT
is not equal to WDB, WDT is used. If WDT is equal to WDB, but YCN is not
equal to YC1 then YCN is used. Otherwise, the value of the VVINIT input
parameter, N, converted to a real, is used. You must initialize Vectors
with a call to VVINIT after modifying this parameter. The default value of
WDT is 0.0.
- XC1 - X Coordinate at Index 1 -
Real
- The parameter XC1 specifies the X coordinate value that corresponds to a
value of 1 for the first subscript of the U, V, vector component arrays as
well as for the P scalar data array, if used. Together with XCM, YC1, and
YCN it establishes the mapping from grid coordinate space to data
coordinate space. If XC1 is equal to XCM, 1.0 will be used. You must
initialize Vectors with a call to VVINIT after modifying this parameter.
The default value of XC1 is 0.0.
- XCM - X Coordinate at Index M -
Real
- The parameter XCM specifies the X coordinate value that corresponds to the
value of the VVINIT input parameter, M, for the first subscript of the U
and V vector component arrays as well as for the P scalar data array, if
used. Together with XC1, YC1, and YCN it establishes the mapping from grid
coordinate space to data coordinate space. If XC1 is equal to XCM, the
value of M, converted to a real, will be used. You must initialize Vectors
with a call to VVINIT after modifying this parameter. The default value of
XCM is 0.0.
- XIN - X Axis Array Increment
(Grid) - Integer
- XIN controls the step size through first dimensional subscripts of the U,V
vector component arrays and also through the P scalar data array if it is
used. For dense arrays plotted at a small scale, you could set this
parameter to a value greater than one to reduce the crowding of the
vectors and hopefully improve the intelligibility of the plot. The grid
point with subscripts (1,1) is always included in the plot, so if XIN has
a value of three, for example, only grid points with first dimension
subscripts 1, 4, 7... (and so on) will be plotted. See also YIN. You must
initialize Vectors with a call to VVINIT after modifying this parameter.
The default value of XIN is 1.
- YC1 - Y Coordinate at Index 1 -
Real
- The parameter YC1 specifies the Y coordinate value that corresponds to a
value of 1 for the first subscript of the U, V, vector component arrays as
well as for the P scalar data array, if used. Together with YCN, XC1, and
XCM it establishes the mapping from grid coordinate space to data
coordinate space. If YC1 is equal to YCN, 1.0 will be used. You must
initialize Vectors with a call to VVINIT after modifying this parameter.
The default value of YC1 is 0.0.
- YCN - Y Coordinate at Index N -
Real
- The parameter YCN specifies the Y coordinate value that corresponds to the
value of the VVINIT input parameter, N, for the second subscript of the U
and V vector component arrays as well as the P scalar data array, if used.
Together with YC1, XC1, and XCM it establishes the mapping from grid
coordinate space to data coordinate space. If YC1 is equal to YCN, the
value of N, converted to a real, will be used. You must initialize Vectors
with a call to VVINIT after modifying this parameter. The default value of
YCN is 0.0.
- YIN - Y Axis Array Increment
(Grid) - Integer
- YIN controls the step size through the second dimension subscripts of the
U and V vector component arrays and also through the P scalar data array
if it is used. For dense arrays plotted at a small scale, you could set
this parameter to a value greater than one to reduce the crowding of the
vectors and hopefully improve the intelligibility of the plot. The grid
point with subscripts (1,1) is always included in the plot, so if YIN has
a value of three, for example, only grid points with second dimension
subscripts 1, 4, 7... (and so on) will be plotted. See also XIN. You must
initialize Vectors with a call to VVINIT after modifying this parameter.
The default value of YIN is 1.
- ZFC - Zero Field Text Block
Color - Integer
- If ZFC is greater or equal to zero, it specifies the GKS color index to
use to color the Zero Field text block. Otherwise the Zero Field text
block is colored using the current GKS text color index. The default value
of ZFC is -1.
- ZFP - Zero Field Text Block
Positioning Mode - Integer
- The ZFP parameter allows you to justify, using any of the 9 standard
justification modes, the Zero Field text block unit with respect to the
position established by the parameters, ZFX and ZFY The position modes are
supported as follows:
- Mode
- Justification
- -4
- The lower left corner of the text block is positioned at ZFX, ZFY.
- -3
- The center of the bottom edge is positioned at ZFX, ZFY.
- -2
- The lower right corner is positioned at ZFX, ZFY.
- -1
- The center of the left edge is positioned at ZFX, ZFY.
- 0 (default)
- The text block is centered along both axes at ZFX, ZFY.
- 1
- The center of the right edge is positioned at ZFX, ZFY.
- 2
- The top left corner is positioned at ZFX, ZFY.
- 3
- The center of the top edge is positioned at ZFX, ZFY.
- 4
- The top right corner is positioned at ZFX, ZFY.
- ZFS - Zero Field Text Block
Character Size - Real
- ZFS specifies the size of the characters used in the Zero Field graphics
text block as a fraction of the viewport width. The default value is
0.033.
- ZFT - Zero Field Text String -
Character* 36
- Use ZFT to modify the text of the Zero Field text block. The Zero Field
text block may appear whenever the U and V vector component arrays contain
data such that all the grid points otherwise eligible for plotting contain
zero magnitude vectors. Currently the string length is limited to 36
characters. Set ZFT to a single space (´ ´) to prevent the
text from being displayed. The default value for the text is ´Zero
Field´.
- ZFX - Zero Field Text Block X
Coordinate - Real
- ZFX establishes the X coordinate of the Zero Field graphics text block as
a fraction of the viewport width. Values less than 0.0 or greater than 1.0
are permissible and respectively represent regions to the left or right of
the viewport. The actual position of the block relative to ZFX depends on
the value assigned to the Zero Field Positioning Mode parameter, ZFP. The
default value is 0.5.
- ZFY - Zero Field Text Block Y
Coordinate - Real
- ZFY establishes the Y coordinate of the minimum vector graphics text block
as a fraction of the viewport height. Values less than 0.0 or greater than
1.0 are permissible and respectively represent regions below and above the
viewport. The actual position of the block relative to ZFY depends on the
value assigned to the Zero Field Positioning Mode parameter, ZFP. The
default value is 0.5.
Online: vectors, vvectr, vvgetc, vvgeti, vvgetr, vvinit, vvrset,
vvsetc, vvseti, vvsetr. vvudmv, vvumxy, ncarg_cbind.
Hardcopy: NCAR Graphics Fundamentals, UNIX Version
Copyright (C) 1987-2009
University Corporation for Atmospheric Research
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