Added normalising constant to DirichletNode$logDensity for consistency with other StochasticNodes.

R/node.R

@@ -286,7 +286,8 @@ DirichletNode <- R6::R6Class(
       self$addParent(alpha, name = 'alpha')
     },
     logDensity = function() {
-      sum((self$parents$alpha$getData() - 1) * log(self$data))
+      lgamma(sum(alpha)) - sum(lgamma(alpha)) +
+        sum((self$parents$alpha$getData() - 1) * log(self$data))
     }
   )
 )