Add stage to produe n-1 plots for a selection

[benkrikler]

From my CMS analysis it's becoming clear how useful a feature it would be to help us optimise event selections. A traditional technique has been to produce so called "n-1" plots, where for each cut in the event selection, you remove that cut and plot the corresponding variable with all the other cuts remaining.

To support this in a single stage, the stage needs to have:

• The full event selection
• Binning parameters for each variable, or at least a default binning scheme
• optionally the name of an output mask for the full event selection.

An alternative might be to just have this stage produce many masks, one per "n-1" cut flow and then we add a mask option to binned dataframes so that we use the existing binned dataframe stages to handle the actual plots. This might give more flexibility and allow for more code re-use.

[seriksen]

Has there been any progress on this?