Cosine Filter for existing Graph

Hello all,

I have been working on filtering an existing graph through a cosine filter in mathcad. I got a txt file (array) into the sheet and started filtering, but the challange that I am facing is the fact that I for an example file that is available to me am using a single current value at one particular point, whereas now in this case I want to filter an entire graph through a cosine filter.

I am confused about the subscripts and can't figure out how to extend them accurately so that the cosine filter performs well. To point this out, Ismpl+spc is a single current value, whereas I am now in contrast working with an actual graph, rather than a single point ont the graph: