Changeset 41e8114 in sasview for realSpaceModeling/pointsmodelpy/libpointsmodelpy

Timestamp:

Nov 2, 2007 11:04:05 AM (17 years ago)

Author:

Mathieu Doucet <doucetm@…>

Branches:

master, ESS_GUI, ESS_GUI_Docs, ESS_GUI_batch_fitting, ESS_GUI_bumps_abstraction, ESS_GUI_iss1116, ESS_GUI_iss879, ESS_GUI_iss959, ESS_GUI_opencl, ESS_GUI_ordering, ESS_GUI_sync_sascalc, costrafo411, magnetic_scatt, release-4.1.1, release-4.1.2, release-4.2.2, release_4.0.1, ticket-1009, ticket-1094-headless, ticket-1242-2d-resolution, ticket-1243, ticket-1249, ticket885, unittest-saveload

Children:

5a2070e

Parents:

7e845ea

Message:

Added error estimation for 2D simulation

Location:

realSpaceModeling/pointsmodelpy/libpointsmodelpy

Files:

• points_model.cc (modified) (1 diff)
• points_model.h (modified) (1 diff)

realSpaceModeling/pointsmodelpy/libpointsmodelpy/points_model.cc

@@ -412 +412 @@
 }
 
+double PointsModel::CalculateIQ_2D_Error(const vector<Point3D>&points, double qx, double qy){
+        
+        int size = points.size();
+
+        double delta_x, delta_y;
+        double q_t2 = qx*qx + qy*qy;
+        double cos_term = 0;
+        double sin_term = 0;
+        double cos_err = 0;
+        double sin_err = 0;
+        
+        // Estimate the error on the position of each point
+        // in x or y as V^(1/3)/N
+        
+        for (int i = 0; i < size; i++) {
+                
+                
+                //the sld for the pair of points
+        
+                double phase = qx*points[i].getX() + qy*points[i].getY();
+                double sld_fac = points[i].getSLD() * points[i].getSLD();
+                
+                cos_term += cos(phase) * points[i].getSLD();
+                sin_term += sin(phase) * points[i].getSLD();
+
+                sin_err += cos(phase) * cos(phase) * sld_fac;
+                cos_err += sin(phase) * sin(phase) * sld_fac;
+        
+        }                       
+
+        // P(q) = 1/V I(q) = (V/N)^2 (1/V) (cos_term^2 + sin_term^2) 
+        // We divide by N here and we will multiply by the density later.
+
+        // We will need to multiply this error by V^(1/3)/N.
+        // We don't have access to V from within this class.
+        return 2*sqrt(cos_term*cos_term*cos_err*cos_err + sin_term*sin_term*sin_err*sin_err)/size;      
+}
+

realSpaceModeling/pointsmodelpy/libpointsmodelpy/points_model.h

@@ -28 +28 @@
   // Fast 2D simulation
   double CalculateIQ_2D(const vector<Point3D>&, double qx, double qy);
+  double CalculateIQ_2D_Error(const vector<Point3D>&, double qx, double qy);
   
   //given a set of points, calculate distance correlation