Never mind - I found the problem. The variables we being read in in the wrong order. Oops!
I am using RooDataSet::read() to read in data from ascii files as a background RooDataSet. For one of my data files, containing 8866 events, the dataset produced only contains 1648 entries. This doesn’t seem to be a problem with variable ranges excluding certain events, and there isn’t any irregularities in the ascii file at the point at which it seems to stop reading in. Deleting events from the file around the point where it stops does not solve the problem.
If I append this problematic data file to the end of another file (signal events, for example), then the total size of the dataset is the size of the signal sample, plus 1648.
Does anyone have any ideas what the problem could be? I’m using RooFit 2.31