Your normality array is an example of a cell array. You can initialize it as
normality_array = cell(num_col,1);
With regards to runtime, if you are referring to this question, I said that "part of the reason" for slowness was preallocation. Depending on your variable sizes, the cost of memory allocation might not be much compared to other factors. There may be other improvements that can be made, but that's a topic for the other question.
Best Answer