Added LogNormalDistribution.

src/qinfer/distributions.py

@@ -262,6 +262,28 @@ def sample(self, n=1):
         z = np.random.randn(n,self._n_rvs)
         return self._ranges[:, 0] +self._weight*z+np.random.rand(n)*self._ranges[:, 1];
 
+class LogNormalDistribution(Distribution):
+    """
+    Log-normal distribution.
+
+    :param mu: Location parameter (numeric), set to 0 by default.
+    :param sigma: Scale parameter (numeric), set to 1 by default.
+                  Must be strictly greater than zero.
+    """
+
+    def __init__(self, mu=0, sigma=1):
+        self.mu = mu # lognormal location parameter
+        self.sigma = sigma # lognormal scale parameter
+
+        self.dist = st.lognorm(sigma,0,mu) # scipy distribution location = 0
+
+    @property
+    def n_rvs(self):
+        return 1
+
+    def sample(self, n=1):
+        return self.dist.rvs(size=n)[:,np.newaxis]
+
 class MVUniformDistribution(object):
 
     def __init__(self, dim = 6):