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CPCNRC(3NCARG) NCAR GRAPHICS CPCNRC(3NCARG)

CPCNRC - Draws black and white contours with a single call. the behavior of the old routine CONREC; it has the same arguments and produces similar output.


CALL CPCNRC (ZDAT, KZDT, MZDT, NZDT, FLOW, FHGH, FINC,
+ NSET, NHGH, NDSH)

#include <ncarg/ncargC.h>

void c_cpcnrc (float *zdat, int kzdt, int mzdt, int nzdt,
float flow, float fhgh, float finc, int nset, int nhgh,
int ndsh)

(REAL array, dimensioned KZDT x n, where "n" is greater than or equal to NZDT, input) is the array containing the data to be contoured.
(INTEGER, input) is the first dimension of the FORTRAN array ZDAT.
(INTEGER, input) is the first dimension of the array of data in ZDAT. MZDT must be less than or equal to KZDT.
(INTEGER, input) is the second dimension of the array of data in ZDAT. NZDT must be less than or equal to the declared second dimension of the array ZDAT.
(REAL, input) is the desired lowest contour level. If FLOW is equal to or greater than FHGH, Conpack will choose the set of contour levels.
(REAL, input) is the desired highest contour level. If FHGH is equal to or less than FLOW, Conpack will choose the set of contour levels.
(REAL, input) says how contour levels are to be chosen. There are two possibilities:
  • If FINC is greater than zero, it specifies the desired contour interval to be used. In this case, if FLOW is less than FHGH, the intervals used will be FLOW, FLOW+FINC, FLOW+2*FINC, ... FLOW+n*FINC, where "n" is the largest integer such that FLOW+n*FINC is less than or equal to FHGH. If FLOW is greater than or equal to FHGH, the contour levels will be those integer multiples of FINC which fall between the minimum value in ZDAT and the maximum value in ZDAT.
  • If FINC is less than or equal to zero, Conpack will choose the contour interval in such a way as to give at least 16 contour levels (if FINC is zero) or MAX(1,INT(-FINC)) contour levels (if FINC is less than zero) between the minimum and maximum values in ZDAT. All the contour levels will be integer multiples of the chosen interval. If FLOW is less than FHGH, no contour lines will be drawn for chosen contour levels which are outside the range (FLOW,FHGH).
(INTEGER, input) says how the contour plot is to be mapped onto the plotter frame. There are three basic possibilities:
  • If the value of NSET, modulo three, is zero, the "standard configuration" will be used. Conpack will be directed to call SET. The portion of the plotter frame bounded by the lines "X=.05", "X=.95", "Y=.05", and "Y=.95" (in the "fractional" or "normalized-device-coordinate" system) will be used. The shape of the plot will be determined by the values of the internal parameters 'WDL', 'WDR', 'WDB', and 'WDT'; by default, the ratio of the plot's width to its height will be MZDT/NZDT. If the ratio of the width to the height is less than 1/4 or greater than 4, the plot will be made square. CPBACK will be called to draw a perimeter.
  • If the value of NSET, modulo three, is equivalent to minus one, the contour plot will fill the current viewport. Conpack will be directed to call SET. The portion of the plotter frame used will be that bounded by the lines "X=xl", "X=xr", "Y=yb", and "Y=yt", where "xl", "xr", "yl", and "yr" are obtained by means of a 

    	CALL GETSET (xl,xr,yl,yr,...)
    The plot will fill this entire area. CPBACK will not be called to draw a perimeter.
  • If the value of NSET, modulo three, is equivalent to plus one, Conpack will be directed not to call SET. It will be assumed that the user has done the appropriate call. CPBACK will not be called to draw a perimeter. Use this option when overlaying CPCNRC output on an existing background (one drawn by Ezmap, for example).
If the value of NSET is -1, 0, or 1, CPCNRC will, prior to returning control to the caller, restore the SET call to what it was on entry (which is how CONREC works). If the value of NSET is less than -1 or greater than 1, CPCNRC will not so restore the SET call; this may be useful if other objects are to be drawn on the plot produced by CPCNRC.
(INTEGER, input) says whether highs and lows or data points are to be labeled. There are three possibilities:
  • If NHGH is zero, each high is marked with an "H" and each low is marked with an "L"; the value is written as a subscript of the "H" or "L".
  • If NHGH is greater than zero, each data point is marked with the value at that point. No attempt is made to cull overlapping values, so using this option when there are too many data points may result in a mess. The values of the Conpack parameters 'HLA' and 'HLS' are retrieved and used to determine the angle at which the values are written and the size of the characters used. They may be used to reduce the clutter somewhat.
  • If NHGH is less than zero, neither of the above is done.
(INTEGER, input) may be used to specify a 10-bit dash pattern to be used. (If ABS(NDSH) is 0, 1, or 1023, all solid lines are used.) If NDSH is greater than zero, the specified dash pattern is used for all contour lines; if NDSH is less than zero, the dash pattern is used only for negative-valued contour lines. Note: the 10-bit pattern is actually made into a 16-bit pattern by appending a copy of the high-order six bits.

The C-binding argument descriptions are the same as the FORTRAN argument descriptions with the following exceptions:

Dimensioned n by kzdt, where n is greater than or equal to nzdt.
The second dimension of the array zdat.
The second dimension of the array of data in zdat. mzdt must be less than or equal to kzdt.
The first dimension of the array of data in zdat. nzdt must be less than or equal to the declared first dimension of the array zdat.

The appearance of the plot produced by CPCNRC may vary, depending on the setting of internal parameters of Conpack. The following should be noted:

  • By default, contour lines will be labeled using the old CONREC scheme of appending the label for a line to the dash pattern for the line. To use one of the new schemes, place a

    CALL CPSETI ('LLP - LINE LABEL POSITIONING',n)

    where n has the value 2 or 3, before the call to CPCNRC. CPCNRC retrieves the value of 'LLP' and, if the value is a 2 or a 3, modifies the calls that it performs so as to properly shield labels from having contour lines drawn through them.

  • By default, high-quality characters will be used in the informational label, in high/low labels, in point-value labels, and in contour-line labels written when 'LLP' is 2 or 3. To use lower-quality characters, place a

    CALL PCSETI ('QUALITY',1)

    or a

    CALL PCSETI ('QUALITY',2)

    prior to the call to CPCNRC.

    Note that these calls are to subroutines that start with the letters PC, because the routine you are calling is in the utility Plotchar. (Conpack uses Plotchar to plot characters.)

  • If the output from CPCNRC is to be overlaid on an Ezmap background and longitude is a linear function of the first subscript of the data array and latitude is a linear function of the second subscript of the data array, you can

Call Ezmap to draw the background.

Set the parameter 'MAP' to 1.

Set the parameters 'XC1', 'XCM', 'YC1', and 'YCN' to specify the longitude and latitude ranges. Note: 'XCM' must be numerically larger than 'XC1'. If, for example, your data run from 175 degrees east of Greenwich at the left edge to 160 degrees west of Greenwich at the right edge (which is -160 degrees east), then you should set 'XC1' = 175 and 'XCM' = 200 to achieve the proper mapping.

Call CPCNRC to draw the contour plot.

  • To smooth the contour lines in the same way that they would have been smoothed by the "smooth" or "super" versions of CONREC, insert

    CALL CPSETR ('T2D - TENSION ON THE 2D SPLINES',t),

    where t is the desired tension, to turn on the smoother.

  • By default, no scale factor is used. (Because Conpack can write contour line labels in scientific notation, it was considered less important to use a scale factor.) If you want to use a scale factor, the value of the internal parameter 'SFS' should be set prior to calling CPCNRC.
  • CPCNRC contains a real workspace array, an integer workspace array, and an area map, which is used to prevent contour lines from passing through labels when 'LLP' has the value 2 or 3. The lengths of these arrays are 5000, 2000, and 12000, respectively. If this proves insufficient, you must obtain a copy of the code for CPCNRC, adjust the dimensions as required, and compile it in place of the default version.
  • Certain internal parameters are used by CPCNRC; user calls to reset them prior to the call to CPCNRC will therefore have no effect. These parameters are as follows:

    'AIA' 'AIB' 'CIS' 'CIU' 'CLC' 'CLD' 'CLL' 'CLS' 'CLV' 'CLU' 'CMN' 'CMX' 'HLT' 'HIT' 'LOT' 'LLC' 'LLT' 'NCL' 'SET' 'VPB' 'VPL' 'VPR' 'VPS' 'VPT'

  • Subroutines with names of the form CPCHxx (the change subroutines) will be of more value when used in conjunction with CPCNRC than when used in conjunction with the more basic Conpack subroutines. For example, the only way to change the color of the zero contour line drawn by a call to CPCNRC is to supply your own version of the routine CPCHCL; there is no way, short of modifying the code of CPCNRC, to use the internal parameter that controls the color of the zero contour line.
  • Like CONREC, CPCNRC does no call to FRAME. To advance the frame, put a CALL FRAME after the call to CPCNRC.

Use the ncargex command to see the following relevant examples: ccpcnrc, cpex09, tconpa.

To use CPCNRC or c_cpcnrc, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.

Online: conpack, cpback, cpchcf, cpchcl, cpchhl, cpchil, cpchll, cpcica, cpclam, cpcldm, cpcldr, cpcltr, cpdrpl, cpezct, cpgetc, cpgeti, cpgetr, cplbam, cplbdr, cpmpxy, cpmviw, cpmvrw, cppkcl, cppklb, cprect, cprset, cpscae, cpsetc, cpseti, cpsetr, cpsps1, cpsps2, ncarg_cbind

Hardcopy: NCAR Graphics Contouring and Mapping Tutorial

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University Corporation for Atmospheric Research

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March 1993 UNIX