plmapline - Plot all or a subset of Shapefile data using
lines in world coordinates
plmapline(mapform, name, minx,
maxx, miny, maxy, plotentries,
nplotentries)
Plot all or a subset of Shapefile data using lines in world
coordinates. Our 19th standard example demonstrates how to use this
function. This function plots data from a Shapefile using lines as in
plmap(3plplot), however it also has the option of also only drawing
specified elements from the Shapefile. The vector of indices of the required
elements are passed as a function argument. The Shapefile data should
include a metadata file (extension.dbf) listing all items within the
Shapefile. This file can be opened by most popular spreadsheet programs and
can be used to decide which indices to pass to this function.
Redacted form: plmapline(mapform, name, minx, maxx, miny, maxy,
plotentries)
This function is used in example 19.
- mapform
(PLMAPFORM_callback(3plplot), input)
- A user supplied function to transform the coordinates given in the
shapefile into a plot coordinate system. By using this transform, we can
change from a longitude, latitude coordinate to a polar stereographic
project, for example. Initially, x[0]..[n-1] are the longitudes and
y[0]..y[n-1] are the corresponding latitudes. After the call to mapform(),
x[] and y[] should be replaced by the corresponding plot coordinates. If
no transform is desired, mapform can be replaced by NULL.
- name
(PLCHAR_VECTOR(3plplot), input)
- An ascii character string specifying the file name of a set of Shapefile
files without the file extension.
- minx
(PLFLT(3plplot), input)
- The minimum x value to be plotted. This must be in the same units as used
by the Shapefile. You could use a very large negative number to plot
everything, but you can improve performance by limiting the area drawn.
The units must match those of the Shapefile projection, which may be for
example longitude or distance. The value of minx must be less than the
value of maxx.
- maxx
(PLFLT(3plplot), input)
- The maximum x value to be plotted. You could use a very large number to
plot everything, but you can improve performance by limiting the area
drawn.
- miny
(PLFLT(3plplot), input)
- The minimum y value to be plotted. This must be in the same units as used
by the Shapefile. You could use a very large negative number to plot
everything, but you can improve performance by limiting the area drawn.
The units must match those of the Shapefile projection, which may be for
example latitude or distance. The value of miny must be less than the
value of maxy.
- maxy
(PLFLT(3plplot), input)
- The maximum y value to be plotted. You could use a very large number to
plot everything, but you can improve performance by limiting the area
drawn.
- plotentries
(PLINT_VECTOR(3plplot), input)
- A vector containing the zero-based indices of the Shapefile elements which
will be drawn. Setting plotentries to NULL will plot all elements
of the Shapefile.
- nplotentries
(PLINT(3plplot), input)
- The number of items in plotentries. Ignored if plotentries
is NULL.
Many developers (who are credited at
http://plplot.org/credits.php) have contributed to PLplot over its long
history.
PLplot documentation at http://plplot.org/documentation.php.