Moved model transforms to different file.

SimPEG/forward/ModelTransforms.py

@@ -0,0 +1,49 @@
+import numpy as np
+
+
+class LogModel(object):
+    """docstring for LogModel"""
+    def modelTransform(self, m):
+        """
+            :param numpy.array m: model
+            :rtype: numpy.array
+            :return: transformed model
+
+            The modelTransform changes the model into the physical property.
+
+            A common example of this is to invert for electrical conductivity
+            in log space. In this case, your model will be log(sigma) and to
+            get back to sigma, you can take the exponential:
+
+            .. math::
+
+                m = \log{\sigma}
+
+                \exp{m} = \exp{\log{\sigma}} = \sigma
+        """
+        return np.exp(mkvc(m))
+
+    def modelTransformDeriv(self, m):
+        """
+            :param numpy.array m: model
+            :rtype: scipy.csr_matrix
+            :return: derivative of transformed model
+
+            The modelTransform changes the model into the physical property.
+            The modelTransformDeriv provides the derivative of the modelTransform.
+
+            If the model transform is:
+
+            .. math::
+
+                m = \log{\sigma}
+
+                \exp{m} = \exp{\log{\sigma}} = \sigma
+
+            Then the derivative is:
+
+            .. math::
+
+                \\frac{\partial \exp{m}}{\partial m} = \\text{sdiag}(\exp{m})
+        """
+        return sdiag(np.exp(mkvc(m)))