Changeset f0ffb873 in sasview

Timestamp:

Feb 28, 2009 10:07:52 AM (16 years ago)

Author:

Jae Cho <jhjcho@…>

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:

acd91458

Parents:

35be99c

Message:

Fixed singularity of the function

File:

• sansmodels/src/sans/models/PowerLawModel.py (modified) (2 diffs)

sansmodels/src/sans/models/PowerLawModel.py

@@ -36 +36 @@
         self.params['background']   = 0.0
         self.description=""" The Power_Law model.
-        F(x) = scale* (x)^(-m) + bkd
+        F(x) = scale* (|x|)^(-m) + bkd
         The model has three parameters: 
         m     =  power
@@ -50 +50 @@
     def _PowerLaw(self, x):
         """
-            Evaluate  F(x) = scale* (x)^(-m) + bkd
+            Evaluate  F(x) = scale* (|x|)^(-m) + bkd
            
         """
-        if x<0 and self.params['m']>0:
-            raise ValueError, "negative number cannot be raised to a fractional power"
-        
-        return self.params['scale']*math.pow(x ,-1.0*self.params['m'])\
+        #if x!=0 and self.params['m']!=0:
+        #   raise ValueError, "negative number cannot be raised to a fractional power"
+        if self.params['m']>0  and x==0:
+            return 1e+32
+        elif self.params['m']==0  and x==0:
+            return 1
+        else:
+            return self.params['scale']*math.pow(x ,-1.0*self.params['m'])\
                 + self.params['background']