| 
            plshades
          ( | a , | 
| nx , | |
| ny , | |
| defined , | |
| xmin , | |
| xmax , | |
| ymin , | |
| ymax , | |
| clevel , | |
| nlevel , | |
| fill_width , | |
| cont_color , | |
| cont_width , | |
| fill , | |
| rectangular , | |
| pltr , | |
| pltr_data ); | 
      Shade regions on the basis of value.  This is the high-level routine
      for making continuous color shaded plots with cmap1 while
      plshade should be used to plot individual shaded regions
      using either cmap0 or cmap1.
      examples/;<language>/x16* shows how to use
      plshades for each of our supported languages.
    
a
          (PLFLT_MATRIX
	    A matrix containing function values to plot.  Should have
	    dimensions of nx by ny.
          
nx
          (PLINTFirst dimension of matrix "a".
ny
          (PLINTSecond dimension of 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).
clevel
          (PLFLT_VECTORA vector containing the data levels corresponding to the edges of each shaded region that will be plotted by this function. To work properly the levels should be monotonic.
nlevel
          (PLINTNumber of shades plus 1 (i.e., the number of shade edge values
	  in clevel
fill_width
          (PLFLTDefines the line width used by the fill pattern.
cont_color
          (PLINTDefines cmap0 pen color used for contours defining edges of shaded regions. The pen color is only temporary set for the contour drawing. Set this value to zero or less if no shade edge contours are wanted.
cont_width
          (PLFLTDefines line width used for contours defining edges of shaded regions. This value may not be honored by all drivers. The pen width is only temporary set for the contour drawing. Set this value to zero or less if no shade edge contours are wanted.
fill
          (PLFILL_callback
            Callback routine used to fill the region.  Use plfill for this purpose.
          
rectangular
          (PLBOOLSet rectangularpltrlrectangularrectangularrectangular
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: plshades(a, defined, xmin, xmax, ymin, ymax, clevel, fill_width, cont_color, cont_width, fill, rectangular, pltr, pltr_data)
          
This function is used in examples 16, 21, and 22.