/*      FILE: fdel.c
 *   PURPOSE: FDEL function for a 2-d Gaussian on a Tilted background 
 *    AUTHOR: Kenneth J. Mighell (mighell@noao.edu)
 *  LANGUAGE: ANSI C
 *      DATE: 2001SEP10
 * COPYRIGHT: (C) 2001 Assoc. of Universities for Research in Astronomy Inc.
 *
 * COMMENT:
 *
 *    MXNPARL=7  
 *  
 *  and
 *
 *    ad[0] is BE (=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 SE (=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"

#define DEBUG (MX_FALSE)

void fdel_v6(
  double xd,      /* X coordinate */
  double yd,      /* Y coordinate */
  double *md_p,   /* Z model */
  double ad[],    /* parameter vector */
  double delad[], /* partial derivative vector */
  long nparl      /* number of parameters */
) {
  char funcnamec[] = "fdel_v6 (TiltedGaussian)";
  double md, dzdi, dzdx, dzdy, dzds;
  const int res=5;
  
  if (7 != MXNPARL) { sprintf( MX.tmpmsg,
    "*** FATAL ERROR *** : (MXNPARL=%ld) != 5\n", MXNPARL);
    goto error;
  }

  if (nparl > MXNPARL) { sprintf( MX.tmpmsg,
    "*** FATAL ERROR *** : (nparl=%ld) != 4\n", nparl);
    goto error;
  }

  if (DEBUG) printf("[1]\n");
  if (DEBUG) fflush(stdout);

  Gaussian2d_v12(
    ad[3], ad[4], ad[5], ad[6], res, xd, yd, &md, &dzdi, &dzdx, &dzdy, &dzds
  );

  if (DEBUG) printf("[2]\n");
  if (DEBUG) fflush(stdout);

  /* model value */
  md += ad[0] + (xd*ad[1]) + (yd*ad[2]); 

  /* del(model)/del(B_0) */
  delad[0] = 1.0;

   /* del(model)/del(B_X) */
  delad[1] = xd; 

  /* del(model)/del(B_Y) */
  delad[2] = yd;                        

  /* del(model)/del(I_0) */
  delad[3] = dzdi;

  /* del(model)/del(X_0) */
  delad[4] = dzdx;

  /* del(model)/del(Y_0) */
  delad[5] = dzdy;

  /* del(model)/del(SIMGA_0) */
  delad[6] = dzds;

  if (DEBUG) printf("[3]\n");
  if (DEBUG) fflush(stdout);

ok:
  goto bye;

error:
  fprintf (stderr, "# %s: %s", funcnamec, MX.tmpmsg);
  exit(1);

bye:
  *md_p = md;
  return;
}
#undef DEBUG
/* end-of-file */