C4W1 Assignment last cell expected output

[balaji.ambresh]

I don’t understand what you mean by:

@Michael_Crabtree

how can the same (saved) notebook go from a grade of 79 to zero?

As far as windowing is concerned, the window size to use is 10. Here’s the relevant text:

@adonaivera

in this case, the time window was ten days, that is why they take a year ago (365 days) and add five days and then retake the 365 days, and now you subtract five days left to finish with a window of 10.

The reason you don’t get an error is because the shapes match when it comes to elementwise operations.