Moving Transform: add "Cumulative count"

[wvdvegte]

Timeseries version

0.6.3

Orange version

3.37.0

Suggested enhancement

Add an option to calculate the cumulative count, i.e., the number of records per aggregated time period. It's a very simple calculation, but currently the only alternative to compute it would be to first add a dummy variable with Formula (numerical, dummy := 1 for every row), then apply Cumsum to it in Moving Transform