Multiclass BDT, number of Test/Training events

Dear all,

I try to use a multi-class BDTG but I cannot set the number of events used for training and testing.

In usual binary BDT I use :
dataloader->PrepareTrainingAndTestTree("", “Random:nTest_Signal=5000:nTest_Background=5000”);

wich does the job. Trying the same thing in BDTG multi-class gives me this error :
: The following options were specified, but could not be interpreted: ‘nTest_Signal=5000:nTest_Background=5000’, please check!

I suppose that this option is not valid in multi-class (and I can understand that) but I do not find an other way that can works within multi-class BDTG.

I am very new in using TMVA and ROOT and I apologize if my question is trivial.

Thanks for your time,

It depends on how you name your input trees.

If you add trees like this:

AddTree(treeClass1, "inputClass1", ...)
AddTree(treeClassN, "inputClassN", ...)

You need to call:
PrepareTrainingAndTestTree("", "nTest_inputClass1=5000:(...):nTest_inputClassN=5000")
I.e. specify the events for every class.

This works perfectly, thank you for your help !