Add logevidence to chain

Author: penelopeysm

ext/DynamicPPLMCMCChainsExt.jl

@@ -166,12 +166,20 @@ function AbstractMCMC.bundle_samples(
         info = merge(info, (start_time=stats.start, stop_time=stats.stop))
     end
 
+    # Calculate logevidence, if it's available
+    logevidence = if :logevidence in names(bare_chain)
+        mean(bare_chain[:logevidence])
+    else
+        missing
+    end
+
     # Reconstruct the chain with the extra information
     # Yeah, this is quite ugly. Blame MCMCChains.
     chain = MCMCChains.Chains(
         bare_chain.value.data,
         names(bare_chain),
         bare_chain.name_map;
+        evidence=logevidence,
         info=info,
         start=discard_initial + 1,
         thin=thinning,