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Asked: 2026-06-17T03:07:59+00:00

It seems like both inf and Inf are exactly same in MATLAB (likewise nan

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It seems like both inf and Inf are exactly same in MATLAB (likewise nan and NaN, but not Nan). Is there any difference?

>> which inf
built-in (/Applications/MATLAB_R2011b.app/toolbox/matlab/elmat/inf)
>> which Inf
built-in (/Applications/MATLAB_R2011b.app/toolbox/matlab/elmat/Inf)

If they are the same, which one should be used in practice? For allocating arrays I have been using x = inf(3,5) style following zeros and ones being all small caps. For assigning single value, I use x = Inf. Do you think this is a consistent use?

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  1. Editorial Team

    Here are the conventions that MATLAB appears to use:

    For Not-a-Number: Always use NaN (Except in combinations such as isnan()

    For Infinite: Use inf for the function and use Inf for the value (and INFs for multiples, but this is not a command of course). Note that this is a bit tricky as it means that the evaluation of inf gives Inf.

    Deduced from:

    help Inf: inf(N) is an N-by-N matrix of INFs.

    help nan: NaN(N) is an N-by-N matrix of NaNs.

    help isnan: For example, isnan([pi NaN Inf -Inf]) is [0 1 0 0].

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