From 62f00004eb1ffde42c593b64848285a584770051 Mon Sep 17 00:00:00 2001
From: rowanc1 <rowan@visiblegeology.com>
Date: Tue, 11 Feb 2014 15:02:30 -0800
Subject: [PATCH] bug fix.

---
 SimPEG/Mesh/TreeMesh.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/SimPEG/Mesh/TreeMesh.py b/SimPEG/Mesh/TreeMesh.py
index 63280076..0cd0cca3 100644
--- a/SimPEG/Mesh/TreeMesh.py
+++ b/SimPEG/Mesh/TreeMesh.py
@@ -893,9 +893,16 @@ class TreeMesh(InnerProducts, BaseMesh):
             self.number()
             # TODO: Preallocate!
             I, J, V = [], [], []
+            # kinda a hack for the 2D gradient
+            # because edges are not stored
             edges = self.faces if self.dim == 2 else self.edges
             for edge in edges:
-                I += [edge.num, edge.num]
+                if self.dim == 3:
+                    I += [edge.num, edge.num]
+                elif self.dim == 2 and edge.faceType == 'x':
+                    I += [edge.num + self.nFy, edge.num + self.nFy]
+                elif self.dim == 2 and edge.faceType == 'y':
+                    I += [edge.num - self.nFx, edge.num - self.nFx]
                 J += [edge.node0.num, edge.node1.num]
                 V += [-1, 1]
             G = sp.csr_matrix((V,(I,J)), shape=(self.nE, self.nN))