# Calculating Energy

I’m a little bit confused about the wording used for the functions `calculate_energy` and `calculate_min_energy_column`. What does `w` stand for?

Assume, we have an entry in the matrix with coordinates (i, j) whereas `i` is the colum and `j` is the row. Then the position in the array is defined by `yx_index(j, i, width)`. Should I consider all entries with `i < w` or `yx_index(j, i, width) < w`?

Hi,

it is very helpful to look at why we need this w. Intuitively, the w tells you how many columns have already been removed. So how many black columns should be at the right boundary.
Thus, `i < w` is the concrete answer to your question.

If you would use `yx_index(j, i, width) < w` you would be ignoring rows of your image (or even only parts of a single row if w is chosen poorly).

I hope this helps you

Lukas

4 Likes