MATLAB: How to extract last non-zero element above current row in same column

Question

Hi everyone,

I'm dealing with a column of quarterly data (shares outstanding in an equities dataset) and need to fill in NaN or 0 elements with the last non-zero entry in a row above in the same column (provided the security is the same – I've got a loop that checks this condition first).

Loops quickly become inefficient for the missing data filling task if i need to check each prior row sequentially. The number of empty cells above is typically two, but it can be quite irregular…could be six, could be more. I don't think 'find' works for this particular task either, but I'm quite new to coding so could be wrong.

I'm sure there must be a very simple solution. Any suggestions?

Best,

Gerry

Answer 1

I think the best way is find as you mentioned.

for i1 = 1:numel(X)
    if any ([isnan(X(i1)); X(i1)==0])
        idx = find (X(1:i1-1),1,'last');
        X(i1) = X(idx);
    end
end