Changeset 1073 for trunk/GSASIIpwd.py

Timestamp:

Oct 1, 2013 3:40:19 PM (10 years ago)

Author:

vondreele

Message:

change chebyschev background fxn to match what is in old GSAS. Much better fits now with it.

File:

• trunk/GSASIIpwd.py (modified) (2 diffs)

trunk/GSASIIpwd.py

@@ -494 +494 @@
             break
     if bakType in ['chebyschev','cosine']:
-        for iBak in range(nBak):    
+        dt = xdata[-1]-xdata[0]    
+        for iBak in range(nBak):
             key = pfx+'Back:'+str(iBak)
             if bakType == 'chebyschev':
-                yb += parmDict[key]*(xdata-xdata[0])**iBak
+                yb += parmDict[key]*(2.*(xdata-xdata[0])/dt-1.)**iBak
             elif bakType == 'cosine':
                 yb += parmDict[key]*npcosd(xdata*iBak)
@@ -579 +580 @@
 
     if bakType in ['chebyschev','cosine']:
+        dt = xdata[-1]-xdata[0]    
         for iBak in range(nBak):    
             if bakType == 'chebyschev':
-                dydb[iBak] = (xdata-xdata[0])**iBak
+                dydb[iBak] = (2.*(xdata-xdata[0])/dt-1.)**iBak
             elif bakType == 'cosine':
                 dydb[iBak] = npcosd(xdata*iBak)