Real Number to N-digit String

num2strN( input , N ) Floors a real number and converts it to an N-digit string.

Floors a real number and converts it to an N-digit string, e.g. for N=3 input 1 becomes 001, 34 becomes 034 and 876 remains the same.
Can be used for various purposes. I wrote it for writing images in a folder such that they have names image001.jpg, image002.jpg, etc. I also used it to display the time in an MM:SS format:

tic
your_code
toc = timeElapsed;
[num2strN(round(timeElapsed/60),3) ':' num2strN(mod(timeElapsed,60),2)]