## NAME

         define_histogram - Enables a user to specify a histogram  in
         terms of a variable 'x'.

## SYNOPSIS

         #include "histogram.h"

         float **define_histogram(int bands, int mode, char **eq)

          <bands> - number of bands in the image
          <mode> - prompt the user for input (mode=1),
                   or use <eq> (mode=0)
          <eq> - string for mapping equation

## PATH

         $CVIPHOME/HISTOGRAM/histogram.c

## DESCRIPTION

         define_histogram is used  to  generate  a  histogram  to  be
         passed  to  the  histogram_spec function.  This function can
         either work interactively when mode = 1, or use  the  string
         to  generate  the histogram when mode = 0. When mode = 1, it
         asks the user to enter an equation in terms of 'x' for  each
         band in the image.

         The following functions may be specified:

         sin(arg)
         cos(arg)
         tan(arg)
         asin(arg)
         acos(arg)
         atan(arg)
         sinh(arg)
         cosh(arg)
         tanh(arg)
         exp(arg)
         ln(arg)
         log(arg)
         sqrt(arg)
         floor(arg)
         ceil(arg)
         abs(arg)
         hypot(arg1,arg2)
         deg(arg)
         rad(arg)
         imp(arg)
         impulse(arg)
         step(arg)
         u(arg)
         ramp(arg)
         r(arg)
         random(low val,high val)

## RETURN VALUES

         On success, this function returns a pointer of pointer to  a
         float,  with  dimensions  float[int][256],  where int is the
         integer passed to the function.

## BUGS

         It could fail if complicated equations are specified.

## SEE ALSO

         get_histogram,        get_histogram_Image,        hist_spec,
         histogram_show,        histogram_spec,       make_histogram,
         showMax_histogram

## AUTHOR

         Copyright (C) 1992, 1996 SIUE - by Scott E.  Umbaugh,  David
         A. Lyons and Yansheng Wei.