Fix sign of XAS

To get the sign of the XAS right (positive absorption peak) we used to look at the name of the channels.

This MR looks at the sign of the average Io and It signal to determine the correct signs.

Closes #61 (closed)

src/toolbox_scs/routines/XAS.py

@@ -174,19 +174,12 @@ def xas(nrun, bins=None, Iokey='SCS_SA3', Itkey='MCP3peaks', nrjkey='nrj',
         """ Select which fields to use as I0 and which to use as I1
         """
 
-        if 'mcp' in Iokey.lower():
-            Io_sign = -1
-        else:
-            Io_sign = 1
-
-        if 'mcp' in Itkey.lower():
-            It_sign = -1
-        else:
-            It_sign = 1
-
         if len(data) == 0:
             return absorption([], [], fluorescence)
         else:
+            Io_sign = np.sign(np.nanmean(data['Io']))
+            It_sign = np.sign(np.nanmean(data['It']))
+            
             return absorption(It_sign*data['It'], Io_sign*data['Io'],
                               fluorescence)