Trouble understanding cidx used in sparse matrices

[Shamika Mohanan]

I'm not able to understand the cidx vector given here- https://www.gnu.org/software/octave/doc/interpreter/Storage-of-Sparse-Matrices.html and here- http://arxiv.org/pdf/cs/0604006v1.pdf

cidx = [0, 1, 2, 2, 4]

I understand why it starts with 0. What does 1, 2, 2, 4 represent?

Shamika