Added Chi-Square routine

aux.py

@@ -41,6 +41,33 @@ class Cycler:
             return self.getCurrent()
         
     
+
+def chisq(r,sigma,redFreedom=0,normalized=False):
+    '''
+    Calculates the chi^2 value of residuals r with standard deviations sigma as
+    is minimized by scipy.optimize.curve_fit. This means it calculates
+    
+        sum( (r/sigma)**2 )
+    
+    if r and sigma are one-dimensional and
+    
+        r.T . sigma^-1 . r
+    
+    if sigma the two-dimensional covariance matrix.
+    
+    If normalized=True, the result is divided by the length of r (Default: False).
+    If redFreedom>0, then normalized=True and the result is divided by len(r)-redFreedom.
+    '''
+    factor=1
+    if redFreedom>0 or normalized:
+        factor=1/(len(r)-redFreedom)
+    if len(np.shape(sigma))==1:
+        return np.sum((r/sigma)**2)*factor
+    elif len(np.shape(sigma)==2) and np.shape(sigma)[0]==np.shape(sigma)[1]:
+        return np.dot(r.T,np.dot(np.linalg.inv(sigma),r))*factor
+    else:
+        raise Exception('Shape of sigma is wrong.')
+
 def makeTuples(iterable):
     
     ret=[]