source: sasview/sansmodels/igor_wrapper/src/weighted_ellipsoid.c @ 7a7dbf4

/**
 * Evaluate EllipsoidModel with angular distribution given
 * by user. 
 * 
 * This code was written as part of the DANSE project
 *  http://danse.us/trac/sans/
 *
 * WARNING: THIS FILE WAS GENERATED BY IGORGENERATOR.PY
 *          DO NOT MODIFY THIS FILE, MODIFY ellipsoid.h
 *          AND RE-RUN THE GENERATOR SCRIPT
 *   
 *  @copyright 2007: University of Tennessee, for the DANSE project
 *
 */

#include "c_disperser.h"
#include "danse.h"
#include <math.h>

/**
 * Evaluate model for given angular distributions in theta and phi.
 * 
 * Angles are in radian.
 * 
 * See disp_ellipsoid.c for more information about the model parameters.
 * 
 * @param dp: model parameters
 * @param phi_values: vector of phi_values
 * @param phi_weights: vector of weights for each entry in phi_values
 * @param n_phi: length of phi_values and phi_weights vectors
 * @param theta_values: vector of theta values
 * @param theta_weights: vector of weights for each entry in theta_values
 * @param n_theta: length of theta_Values and theta_weights vectors
 * @param q: q-value to evaluate the model at
 * @param phi_q: angle between the q-vector and the q_x axis
 * @return: scattering intensity
 * 
    // List of default parameters:
    //         pars[0]:   scale           = 1.0 
    //         pars[1]:   radius_a        = 20.0 A
    //         pars[2]:   radius_b        = 400.0 A
    //         pars[3]:   contrast        = 3e-06 A-2
    //         pars[4]:   background      = 0.0 cm-1
    //         pars[5]:   axis_theta      = 1.57 rad
    //         pars[6]:   axis_phi        = 0.0 rad

    //         pars[7]:   dispersion of radius_a
    //         pars[8]:   dispersion of radius_b
    //         pars[9]:   dispersion of axis_theta
    //         pars[10]:   dispersion of axis_phi
    //         pars[11]:   number of points in dispersion curve
 * 
 * NOTE: DO NOT USE THETA AND PHI PARAMETERS WHEN
 *       USING THIS FUNCTION TO APPLY ANGULAR DISTRIBUTIONS.
 * 
 */
double ellipsoid_Weights(double dp[], double *phi_values, double *phi_weights, int n_phi, 
                                                                double *theta_values, double *theta_weights, int n_theta, 
                                                                double q, double phi_q) {
        // Copy of parameters
        double pars[12];
        // Parameter index for theta
        int theta_index = 5;
        // Parameter index for phi
        int phi_index   = 6;
        int i, i_theta;
        double sum, norm;
        
        // Copy parameters because they will be modified
        for(i=0; i<12; i++) {
                pars[i] = dp[i];
        }

        if (n_theta == 0) {
                return weight_dispersion( &disperse_ellipsoid_analytical_2D,
                                phi_values, phi_weights, n_phi, phi_index, pars, q, phi_q );
        } else {
                sum = 0.0;
                norm = 0.0;
                
                for(i_theta=0; i_theta<n_theta; i_theta++) {
                        // Assign new theta value
                        pars[theta_index] = theta_values[i_theta];
                        // Evaluate the function, weight by sin(theta) 
                        sum += sin(theta_values[i_theta]) * theta_weights[i_theta] * 
                                        weight_dispersion( &disperse_ellipsoid_analytical_2D,
                                        phi_values, phi_weights, n_phi, phi_index, pars, q, phi_q );
                        // Keep track of normalization
                        norm += theta_weights[i_theta];
                }
                
                // Protect against null weight vector
                if(norm > 0) {
                        return sum/norm;
                }
        }
        return 0.0;
}