sig2posSe.c
c99f2e455a51gridgradient_gilles

sig2posSe.c
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			#include<stdio.h>
			#include<math.h>
			#include<fonction.h>
			#include<constant.h>
			#include<dimension.h>
			#include<structure.h>

			/****************************************************************/
			/* nom: sig2posSe */
			/* auteur: Eric Jullo */
			/* date: 01/07 */
			/* place: Marseille */
			/****************************************************************
			* Assuming that the deflection angle is linear between the observed
			* and predicted image, it is possible to analytically relate the
			* image plane chi2 to the source plane chi2.
			*
			* chi2_img = (xi - xiobs) = (xs - bar(xs)) / (1 - d2xxPhi)
			*
			* The observational uncertainties are the image ellipticities a & b.
			*
			* Global variables used :
			*
			*/
			void sig2posSe(struct galaxie multi, double sigx2, double *sigy2)
			{

			struct matrix grad2;

			grad2 = e_grad2_gal(multi, NULL);
			grad2.a /= multi->dos;
			grad2.c /= multi->dos;
			sigx2 = (1. - grad2.a) (1. - grad2.a) * multi->E.a * multi->E.a;
			sigy2 = (1. - grad2.c) (1. - grad2.c) * multi->E.b * multi->E.b;
			}