diff --git a/GPy/core/transformations.py b/GPy/core/transformations.py
index be8c3030..8982e939 100644
--- a/GPy/core/transformations.py
+++ b/GPy/core/transformations.py
@@ -6,18 +6,18 @@ import numpy as np
 
 class transformation(object):
     def __init__(self):
-        #set the domain. Suggest we use 'positive', 'bounded', etc
+        # set the domain. Suggest we use 'positive', 'bounded', etc
         self.domain = 'undefined'
     def f(self, x):
         raise NotImplementedError
 
-    def finv(self,x):
+    def finv(self, x):
         raise NotImplementedError
 
-    def gradfactor(self,f):
+    def gradfactor(self, f):
         """ df_dx evaluated at self.f(x)=f"""
         raise NotImplementedError
-    def initialize(self,f):
+    def initialize(self, f):
         """ produce a sensible initial values for f(x)"""
         raise NotImplementedError
     def __str__(self):
@@ -25,61 +25,92 @@ class transformation(object):
 
 class logexp(transformation):
     def __init__(self):
-        self.domain= 'positive'
-    def f(self,x):
+        self.domain = 'positive'
+    def f(self, x):
         return np.log(1. + np.exp(x))
-    def finv(self,f):
+    def finv(self, f):
         return np.log(np.exp(f) - 1.)
-    def gradfactor(self,f):
+    def gradfactor(self, f):
         ef = np.exp(f)
-        return (ef - 1.)/ef
-    def initialize(self,f):
+        return (ef - 1.) / ef
+    def initialize(self, f):
+        return np.abs(f)
+    def __str__(self):
+        return '(+ve)'
+
+class logexp_clipped(transformation):
+    def __init__(self):
+        self.domain = 'positive'
+    def f(self, x):
+        f = np.log(1. + np.exp(x))
+        return f
+    def finv(self, f):
+        return np.log(np.exp(f) - 1.)
+    def gradfactor(self, f):
+        ef = np.exp(f)
+        gf = (ef - 1.) / ef
+        return np.where(f < 1e-6, 0, gf)
+    def initialize(self, f):
         return np.abs(f)
     def __str__(self):
         return '(+ve)'
 
 class exponent(transformation):
     def __init__(self):
-        self.domain= 'positive'
-    def f(self,x):
+        self.domain = 'positive'
+    def f(self, x):
         return np.exp(x)
-    def finv(self,x):
+    def finv(self, x):
         return np.log(x)
-    def gradfactor(self,f):
+    def gradfactor(self, f):
         return f
-    def initialize(self,f):
+    def initialize(self, f):
         return np.abs(f)
     def __str__(self):
         return '(+ve)'
 
 class negative_exponent(transformation):
     def __init__(self):
-        self.domain= 'negative'
-    def f(self,x):
+        self.domain = 'negative'
+    def f(self, x):
         return -np.exp(x)
-    def finv(self,x):
+    def finv(self, x):
         return np.log(-x)
-    def gradfactor(self,f):
+    def gradfactor(self, f):
         return f
-    def initialize(self,f):
+    def initialize(self, f):
         return -np.abs(f)
     def __str__(self):
         return '(-ve)'
 
+class square(transformation):
+    def __init__(self):
+        self.domain = 'positive'
+    def f(self, x):
+        return x ** 2
+    def finv(self, x):
+        return np.sqrt(x)
+    def gradfactor(self, f):
+        return 2 * np.sqrt(f)
+    def initialize(self, f):
+        return np.abs(f)
+    def __str__(self):
+        return '(+sq)'
+
 class logistic(transformation):
-    def __init__(self,lower,upper):
-        self.domain= 'bounded'
+    def __init__(self, lower, upper):
+        self.domain = 'bounded'
         assert lower < upper
         self.lower, self.upper = float(lower), float(upper)
         self.difference = self.upper - self.lower
-    def f(self,x):
-        return self.lower +  self.difference/(1.+np.exp(-x))
-    def finv(self,f):
+    def f(self, x):
+        return self.lower + self.difference / (1. + np.exp(-x))
+    def finv(self, f):
         return np.log(np.clip(f - self.lower, 1e-10, np.inf) / np.clip(self.upper - f, 1e-10, np.inf))
-    def gradfactor(self,f):
-        return (f-self.lower)*(self.upper-f)/self.difference
-    def initialize(self,f):
-        return self.f(f*0.)
+    def gradfactor(self, f):
+        return (f - self.lower) * (self.upper - f) / self.difference
+    def initialize(self, f):
+        return self.f(f * 0.)
     def __str__(self):
-        return '({},{})'.format(self.lower,self.upper)
+        return '({},{})'.format(self.lower, self.upper)