A bug in generating lag features

[anhquan0412]

There is a bug in week 4 programming assignment notebook where you generate lag features
'After creating a grid, we can calculate some features. We will use lags from [1, 2, 3, 4, 5, 12] months ago.'

The lag features are correct for only target_lag_{} (target_lag_1,2,3 ...) and incorrect for any other lag features.

I documented that bug and the fix in here. Fixing this bug helps me boost my score in LB tremendously.
https://gist.github.com/anhquan0412/330494b051f74eacad3917f43e3ba43a

[aguschin]

Great! Thank you for finding this out.