Function:      dmatrix

Purpose:       Allocate space for a matrix with subscript range
               M[ylo..yhi][xlo..xhi] for doubles.
               
Category:      UTILITY

File:          matrix.c

Author:        M. Vogelaar 

Use:           double **dmatrix( int xlo, int ylo, int xhi, int yhi );

                        
               dmatrix : Output pointer to array of pointers to array
                         of doubles.
                         e.g. the matrix M[ylo..yhi][xlo..xhi]
               xlo     : First subscript in x
               ylo     : First subscript in y               
               xhi     : Last subscript in x
               yhi     : Last subscript in y
                 
                
Example:       double      **image;
 
               image = dmatrix( blo[0], blo[1], bhi[0], bhi[1] );
               x = 3; y = 0;
               element = M[y][x];
               freedmatrix( blo[0], blo[1] );

Comment:       This routine is NOT callable from FORTRAN.

Notes:         After freeing memory with 'freedmatrix' the pointer to
               the matrix is NOT reset to NULL.
               
Updates:       28 Jul,  2000: VOG, Document created.