Fixed Rop of argmax that caused test to fail

theano/tensor/basic.py

@@ -1884,7 +1884,22 @@ class MaxAndArgmax(Op):
     def R_op(self, inputs, eval_points):
         if eval_points[0] is None:
             return [None, None]
-        return [self.make_node(eval_points[0], inputs[1]).outputs[0], None]
+        if not isinstance(inputs[1], theano.Constant):
+            raise ValueError( ('R_op supported for arg_max only for '
+                               'constant axis!'))
+        if inputs[1].data > 1:
+            raise ValueError( ('R_op supported for arg_max only when '
+                               ' axis is 0 or 1'))
+        if inputs[0].ndim != 2:
+            raise ValueError( ('R_op supported for arg_max only when '
+                               ' input is a matrix'))
+        max_vals, max_pos = self.make_node(*inputs).outputs
+        if inputs[1].data == 0:
+            return [eval_points[0][max_pos, arange(eval_points[0].shape[1])], None]
+        else:
+            return [eval_points[0][arange(eval_points[0].shape[0]),
+                                   max_pos], None]
+
 
 
     def grad(self, inp, grads):