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I am trying to create a looping function that takes 252 rows of a matrix from 1, then the next 252 rows of a matrix from 1+1, so on and so forth until nrow of the matrix. I am using the for + if loop combo but I seem to be stuck on the if portion. I'm trying to code if so that if the row is less than the last row in matrix ret, it will keep running, else break. Here is what I have so far: