Convert index to Excel A1 notation

Convert index to Excel A1 notation used in xlswrite

This function translates an index to the Excel A1 notation that is used in xlswrite.

%%%
function a1String = idx2A1(idx)

alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';

if idx < 27
a1String = alphabet(idx);
else
idx2 = rem(idx,26);
if idx2 == 0
a1String = [alphabet(floor(idx/26)-1),'Z'];
else
a1String = [alphabet(floor(idx/26)),alphabet(idx2)];
end
end
%%%