flags vector must be [1,0,1,1,1,0,0] - looks like it is missing a '1' for the 4th row start?

in step three, the first 2x1 should be highlighted : )

How is the row_starts equal to [0,2,3,4]

Oh got it!!

@paavni Could you explain how you get [0,2,3,4]? row_starts = [0,1,2,3] still seems to make more sense to me

As far as I understood the row_starts matrix takes the column matrix and tells the indices where the elements of the column change rows.

Consider the matrix cols = [[0,2],[1],[2],[1,2,3]] which might be represented as [0,2,1,2,1,2,3] The row_starts then gives [0,2,3,4] indicating the row separation

@paavni Got it! Thanks!