| 
            plshade
          ( | a , | 
| nx , | |
| ny , | |
| defined , | |
| xmin , | |
| xmax , | |
| ymin , | |
| ymax , | |
| shade_min , | |
| shade_max , | |
| sh_cmap , | |
| sh_color , | |
| sh_width , | |
| min_color , | |
| min_width , | |
| max_color , | |
| max_width , | |
| fill , | |
| rectangular , | |
| pltr , | |
| pltr_data ); | 
Shade individual region on the basis of value.  Use plshades
    if you want to shade a number of contiguous regions using continuous
    colors.  In particular the edge contours are treated properly in
    plshades.  If you attempt to do contiguous regions with plshade
    the contours at the edge of the shade are partially obliterated by
    subsequent plots of contiguous shaded regions.
a
          (PLFLT_MATRIX
	    A matrix containing function values to plot.  Should have
	    dimensions of nx by ny.
          
nx
          (PLINTFirst dimension of the matrix "a".
ny
          (PLINTSecond dimension of the matrix "a".
defined
          (PLDEFINED_callbackCallback function specifying the region that should be plotted in the shade plot. This function accepts x and y coordinates as input arguments and must return 1 if the point is to be included in the shade plot and 0 otherwise. If you want to plot the entire shade plot (the usual case), this argument should be set to NULL.
xmin, xmax, ymin, ymax
          (PLFLTSee the discussion of pltr
	  below for how these arguments are used (only for the special case when
	  the callback function pltr is not
	  supplied).
shade_min
          (PLFLT
            Defines the lower end of the interval to be shaded. If
            shade_max ≤ shade_min, plshade does nothing.
          
shade_max
          (PLFLT
            Defines the upper end of the interval to be shaded. If
            shade_max ≤ shade_min,
            plshade does nothing.
          
sh_cmap
          (PLINT
            Defines color map. If
            sh_cmap=0sh_colorsh_cmap=1sh_color
sh_color
          (PLFLTDefines color map index with integer value if cmap0 or value in range (0.0-1.0) if cmap1.
sh_width
          (PLFLTDefines width used by the fill pattern.
min_color
          (PLINTDefines pen color, width used by the boundary of shaded region. The min values are used for the shade_min boundary, and the max values are used on the shade_max boundary. Set color and width to zero for no plotted boundaries.
min_width
          (PLFLTDefines pen color, width used by the boundary of shaded region. The min values are used for the shade_min boundary, and the max values are used on the shade_max boundary. Set color and width to zero for no plotted boundaries.
max_color
          (PLINTDefines pen color, width used by the boundary of shaded region. The min values are used for the shade_min boundary, and the max values are used on the shade_max boundary. Set color and width to zero for no plotted boundaries.
max_width
          (PLFLTDefines pen color, width used by the boundary of shaded region. The min values are used for the shade_min boundary, and the max values are used on the shade_max boundary. Set color and width to zero for no plotted boundaries.
fill
          (PLFILL_callback
            Routine used to fill the region.  Use plfill.  Future version of
            PLplot may have other fill routines.
          
rectangular
          (PLBOOL
            Set 
               to true
            if rectangles map to rectangles after coordinate transformation
            with rectangular
            pltrlrectangularrectangularrectangular
pltr
          (PLTRANSFORM_callback A callback function that defines the transformation
	  between the zero-based indices of the matrix
	  apltr is not supplied (e.g., is set to NULL
	  in the C case), then the x indices of
	  axmin through xmax and
	  the y indices of aymin through
	  ymax.
For the C case, transformation functions are provided
	  in the PLplot library: pltr0 for the identity mapping, and pltr1
	  and pltr2 for arbitrary mappings respectively defined by vectors and
	  matrices.  In addition, C callback routines for the transformation can
	  be supplied by the user such as the mypltr function
	  in examples/c/x09c.c which provides a general
	  linear transformation between index coordinates and world
	  coordinates.
For languages other than C you should consult Part III, “ Supported computer languages ” for the details concerning how
	  PLTRANSFORM_callback arguments are interfaced.
	  However, in general, a particular pattern of
	  callback-associated arguments such as a tr vector
	  with 6 elements; xg and yg
	  vectors; or xg and yg matrices
	  are respectively interfaced to a linear-transformation routine similar
	  to the above mypltr function; pltr1; and pltr2.
	  Furthermore, some of our more sophisticated bindings (see, e.g., Chapter 10, Fortran Language) support native language callbacks for handling
	  index to world-coordinate transformations.  Examples of these various
	  approaches are given in
	  examples/<language>x09*,
	  examples/<language>x16*,
	  examples/<language>x20*,
	  examples/<language>x21*, and
	  examples/<language>x22*, for all our
	  supported languages.
pltr_data
          (PLPointer
            Extra parameter to help
            pass information to pltr0, pltr1, pltr2, or whatever routine
            that is externally supplied.
          
Redacted form:
            General: plshade(a, defined, xmin, xmax, ymin, ymax, shade_min, shade_max, sh_cmap, sh_color, sh_width, min_color, min_width, max_color, max_width, fill, rectangular, pltr, pltr_data)
          
This function is used in example 15.