[Rivet] adding histograms

[Robert King]

Hi Rivet Experts,

I expect this is a simple question, but I couldn't see how to do it. I
want to generate a large MC sample and create histograms using Rivet.
I do this by splitting the job up into 100 sub jobs. I then want to
add the histograms that are made for each subjob into one histogram. I
suppose I could convert the .adia files to root files and add together
in root but I hoped there might be a method in Rivet already for doing
this...

Thanks for you advice

Robert