more fixes

nifty5/library/inverse_gamma_operator.py

@@ -50,4 +50,4 @@ def InverseGammaOperator(domain, alpha, q, delta=0.001):
         distance between sampling points for linear interpolation.
     """
     func = lambda x: np.log(invgamma.ppf(norm.cdf(x), alpha))
-    return InterpolatingOperator(domain, func, (-8.2,8.2), delta)
+    return InterpolatingOperator(domain, func, (-8.2,8.2), delta).exp()

nifty5/operators/interpolating_operator.py

@@ -67,14 +67,14 @@ class InterpolatingOperator(Operator):
         # Operator
         fi = np.floor(val).astype(int)
         w = val - fi
-        res = np.exp((1 - w)*self._table[fi] + w*self._table[fi + 1])
+        res = (1 - w)*self._table[fi] + w*self._table[fi + 1]
 
         points = Field.from_local_data(self._domain, res)
         if not lin:
             return points
 
         # Derivative of linear interpolation
-        der = self._deriv[fi]*res
+        der = self._deriv[fi]
 
         jac = makeOp(Field.from_local_data(self._domain, der))
         jac = jac(x.jac)