--- a/python/utils.py	Wed May 08 00:19:28 2013 +0200
+++ b/python/utils.py	Thu May 09 04:02:46 2013 +0200
@@ -287,17 +287,18 @@
 # plotting section
 #########################
 
-def stepPlot(X, firstX, lastX, initialCount = 0):
-    '''for each value in x, increment by one the initial count
+def stepPlot(X, firstX, lastX, initialCount = 0, increment = 1):
+    '''for each value in X, increment by increment the initial count
     returns the lists that can be plotted 
-    to obtain a step plot increasing by one for each value in x, from first to last value'''
+    to obtain a step plot increasing by one for each value in x, from first to last value
+    firstX and lastX should be respectively smaller and larger than all elements in X'''
     
     sortedX = []
     counts = [initialCount]
     for x in sorted(X):
         sortedX += [x,x]
         counts.append(counts[-1])
-        counts.append(counts[-1]+1)
+        counts.append(counts[-1]+increment)
     counts.append(counts[-1])
     return [firstX]+sortedX+[lastX], counts