--- a/python/utils.py	Fri Jul 13 17:08:31 2012 -0400
+++ b/python/utils.py	Fri Jul 13 17:30:25 2012 -0400
@@ -164,6 +164,14 @@
 # maths section
 #########################
 
+def sortXY(X,Y):
+    'returns the sorted (x, Y(x)) sorted on X'
+    D = {}
+    for x, y in zip(X,Y):
+        D[x]=y
+    xsorted = sorted(D.keys())
+    return xsorted, [D[x] for x in xsorted]
+
 def ceilDecimals(v, nDecimals):
     '''Rounds the number at the nth decimal
     eg 1.23 at 0 decimal is 2, at 1 decimal is 1.3'''