
plshades: Shade regions on the basis of value 

DESCRIPTION:

	Shade regions on the basis of value.  This is the high-level routine
	for making continuous color shaded plots with cmap1 while plshade (or
	plshade1) are used for individual shaded regions using either cmap0 or
	cmap1. examples/c/x16c.c shows a number of examples for using this
	function. See the following discussion of the arguments and the PLplot
	documentation for more information.    

SYNOPSIS:

plshades(a, nx, ny, defined, xmin, xmax, ymin, ymax, clevel, nlevel, fill_width, cont_color, cont_width, fill, rectangular, pltr, pltr_data)

ARGUMENTS:

    a (PLFLT **, input) :     Contains ** pointer to array to be plotted.
        The array must have been declared as PLFLT a[nx][ny]. 

    nx (PLINT, input) :    First dimension of array "a". 

    ny (PLINT, input) :    Second dimension of array "a". 

    defined (PLINT (*) (PLFLT, PLFLT), input) :    User function
        specifying regions excluded from the shading plot.    This function
        accepts x and y coordinates as input arguments and must return 0
        if the point is in the excluded region or 1 otherwise. This
        argument can be NULL if all the values are valid. 

    xmin (PLFLT, input) :     Defines the "grid" coordinates.  The data
        a[0][0] has a position of (xmin,ymin). 

    xmax (PLFLT, input) :     Defines the "grid" coordinates.  The data
        a[0][0] has a position of (xmin,ymin). 

    ymin (PLFLT, input) :     Defines the "grid" coordinates.  The data
        a[0][0] has a position of (xmin,ymin). 

    ymax (PLFLT, input) :     Defines the "grid" coordinates.  The data
        a[0][0] has a position of (xmin,ymin). 

    clevel (PLFLT *, input) :     Pointer to array 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 (PLINT, input) :    Number of shades plus 1 (i.e., the number
        of shade edge values in nlevel). 

    fill_width (PLINT, input) :    Defines width used by the fill pattern. 

    cont_color (PLINT, input) :    Defines 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 (PLINT, input) :    Defines pen 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 (void (*) (PLINT, PLFLT *, PLFLT *), input) :      Routine used to
        fill the region.  Use plfill.  Future version of plplot may have
        other fill routines. 

    rectangular (PLINT, input) :    Set rectangular to 1 if rectangles map
        to rectangles after coordinate transformation with pltrl. 
        Otherwise, set rectangular to 0. If rectangular is set to 1,
        plshade tries to save time by filling large rectangles.  This
        optimization fails if the coordinate transformation distorts the
        shape of rectangles. For example a plot in polor coordinates has
        to have rectangular set to 0. 

    pltr (void (*) (PLFLT, PLFLT, PLFLT *, PLFLT *, PLPointer) , input) : 
          Pointer to function that defines transformation between indices
        in array z and the world coordinates (C only).    Transformation
        functions are provided in the PLplot library: pltr0 for identity
        mapping, and pltr1 and pltr2 for arbitrary mappings respectively
        defined by one- and two-dimensional arrays.  In addition,
        user-supplied routines for the transformation can be used as well.
         Examples of all of these approaches are given in the PLplot
        documentation. The transformation function should have the form
        given by any of pltr0, pltr1, or pltr2. 

    pltr_data (PLPointer, input) :      Extra parameter to help pass
        information to pltr0, pltr1, pltr2, or whatever routine that is
        externally supplied. 
