Question

I have a column with only whole numbers in it, to which I need to append a number (say 11) at the front –

data = (1:1300000)';
% append 11 to these numbers

newdata = [111 ;  112 ; 113 ; 114 ; ......]

Is there a way to do it without using str2num (due to speed issues) ? Thanks.

Answer 1

If you take the base 10 logarithm of data, you can find out by how much you have to multiply 11 so that you can turn this into a simple addition.

%# create some test data
data = [1 22 123];

%# add 11*10^x to data so that the two ones end up in front of the number
newData = 11*10.^(floor(log10(data))+1)+data

newData =
         111        1122       11123