| 
            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, 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.
    
mapform
          (PLMAPFORM_callbackA 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_VECTORAn ascii character string specifying the file name of a set of Shapefile files without the file extension.
minx
          (PLFLTThe 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
          (PLFLTThe 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
          (PLFLTThe 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
          (PLFLTThe 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
            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
            The number of items in plotentries.  Ignored if
            plotentries is NULL.
          
      Redacted form: plmapline(mapform, name, minx, maxx, miny, maxy, plotentries)
    
This function is used in example 19.