added along rows and columns in X.sum() for better understanding

[toheedakhtar]

In Reduction - added "along rows" in X.sum(axis=1) and "along columns" in X.sum(axis = 0) , for better understanding and solving confusion.

[toheedakhtar]

added for better understanding in nparray.sum() axis = 0 means along the column and axis = 1 means working along the row. stackoverflow

[smith-kyle]

Just a heads up, you can review notebook changes like this using GitNotebooks.

e.g. this pull request https://gitnotebooks.com/jonkrohn/ML-foundations/pull/10

It's free for public repos, so might be helpful for y'all.