/*      FILE: fdelss.c
 *   PURPOSE: Compute del(model)/del(I_0) [= PSF at (X_0,Y_0) ]
 *    AUTHOR: Kenneth J. Mighell (mighell@noao.edu)
 *  LANGUAGE: ANSI C
 *      DATE: 2001SEP10
 * COPYRIGHT: (C) 2001 Assoc. of Universities for Research in Astronomy Inc.
 *
 * COMMENT: *** ANALYTICAL ***
 *
 *    MXNPARL=7  
 *  
 *  and
 *
 *    ad[0] is B0 (=B_0      constant value of background )
 *    ad[1] is BX (=B_X      X slope value of background )
 *    ad[2] is BY (=B_Y      Y slope value of background )
 *    ad[3] is S0 (=I_0      intensity of 2-d Gaussian )
 *    ad[4] is SX (=X_0      X coordinate of 2-d Gaussian )
 *    ad[5] is SY (=Y_0      Y coordiante of 2-d Gaussian )
 *    ad[6] is SS (=SIGMA_0  standard deviation of 2-d Gaussian )
 *
 *  where
 *
 *    Z = B_0 + + (X*B_X) + (Y*B_Y) + I_0*Gaussian( X, Y; X_0, Y_0, SIGMA_0)
 *
 *  is a Gaussian centered at (X_0,Y_0) on a tilted background
 *
 */

#include "mx.h"
#include "inc.h"

int fdelss_i6(
  double **matrix,
  double **xmatrix,
  double **ymatrix,
  int nx,
  int ny,
  double ad[]
)
{
  int
    status,
    xi,
    yi;
  const int res=5;
  double md, dzdi, dzdx, dzdy, dzds;

  for (yi=0; yi<ny; yi++) {
    for (xi=0; xi<nx; xi++) {
      Gaussian2d_v12(
	ad[3], 
        ad[4], 
        ad[5], 
        ad[6], 
        res, 
        xmatrix[yi][xi],
        ymatrix[yi][xi],
	&md, 
        &dzdi, 
        &dzdx, 
        &dzdy, 
        &dzds
      );
      matrix[yi][xi] = dzds;

    }
  }
bye:
  status=0;
error:
  return(status);
}
/* end-of-file */