improved SimpleLikelihood

imagine/likelihoods/simple_likelihood/simple_likelihood.py

 # -*- coding: utf-8 -*-
 
-import numpy as np
-
 from imagine.likelihoods.likelihood import Likelihood
 
 
 class SimpleLikelihood(Likelihood):
-    def __init__(self, measured_data):
+    def __init__(self, measured_data, data_covariance_operator=None):
         self.measured_data = measured_data
+        self.data_covariance_operator = data_covariance_operator
 
     def __call__(self, observable):
-        shape = observable.shape
         data = self.measured_data.val.get_full_data()
-        obs = observable.val.get_full_data()
-
-        quadratic_diff = ((data - obs).conjugate() * (data - obs)).sum()
-        quadratic_diff /= np.prod(shape)
+        obs_mean = observable.ensemble_mean().val.get_full_data()
 
-        return -quadratic_diff
+        diff = data - obs_mean
+        if self.data_covariance_operator is not None:
+            right = self.data_covariance_operator.inverse_times(diff)
+        else:
+            right = diff
+        return -0.5 * diff.conjugate().vdot(right)