# Using a specific number of digits

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John Carroll on 28 Oct 2022
Commented: John Carroll on 31 Oct 2022
I am looking for a way to fix the number of digital in an array. I am attempting to run a for loop in the form "for k = 1:N where n will be an interger typically between 10 and 200. However as it counts through the loop it will report k as 1, 2, 3 etc. I would like to force k to be three digits such as k = [001 002 003.....010 011 012......100 101 102]
Is there a simple way to do this?
Thanks you

John D'Errico on 28 Oct 2022
Edited: John D'Errico on 28 Oct 2022
Are numbers typically written with leading zero digits? (NO. At least not in anything I've ever done.) The number 001 is no different from the number 1. As such MATLAB returns it as that. No leading digits, at least not if you want it in a numeric form.
Can you force MATLAB to convert an integer so it always return leading zero digits if they would be there? Not as a number. Sorry. But if you want the result to be in a character form, you could do this:
x = 12;
dec2base(x,10,3)
ans = '012'
That will force it to always prepend leading zero digits, so there are always 3 digits shown. HOWEVER, the result is NOT a number. It is just a string of characters at this point..
John Carroll on 29 Oct 2022
The number is part of a file name and always shows as a three digit number so 1 is 001 and 10 is 010 then a three digit number is just 100 and so on.
Stephen23 on 29 Oct 2022
"The number is part of a file name ..."
You should have mentioned this important information in your question. As John D'Errico correctly wrote, numeric types do not store leading zeros, but this is trivial to achieve using SPRINTF et al.

Jeff Miller on 28 Oct 2022
Maybe by "report k" you are referring to printing it, in which case this should work
for k=1:100
fprintf('%03d\n',k)
end
Stephen23 on 29 Oct 2022
Much better without the text concatenation and newline character:
fname = sprintf('MyFile%03d.mat',k);
John Carroll on 31 Oct 2022
This seems to work as well. Thanks.

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