MATLAB Answers

Walter Roberson

array dimensions equivalence check?

Asked by Walter Roberson
on 4 Jan 2012
Latest activity Edited by Walter Roberson
on 21 Sep 2016 at 20:01

You would think I would know this by now, but I never had reason to program it before.

Is there a good idiom for efficiently checking that two arrays are the same size or are row and column vectors of the same length?

For example, this kind of check would be used to find out whether two arrays are assignment-compatible, or to find out if two arrays are compatible for plot() purposes.

The code I have come up with feels overly complicated:

szA = size(A);
szB = size(B);
if isequal(szA,szB) || ...
   (sum(szA==1) == 1 && sum(szB==1) == 1 && ... 
    numel(szA)==2 && numel(szB)==2) && ...
    prod(szA) == prod(szB))

Which is to say, the sizes can be identical, or they can both be 2 dimensional with exactly one of the dimensions of each being 1, and the number of elements the same between the two.

This kind of check must be programmed all over the place. Perhaps there is a utility routine that I overlooked?

  1 Comment

Paulo Abelha
on 21 Sep 2016 at 12:09

Hello Walter,

I have implemented a function that might help you:

Best regards,



1 Answer

Answer by David Young
on 4 Jan 2012
 Accepted answer

One alternative:

isequal(size(A), size(B)) || (isvector(A) && isvector(B) && numel(A) == numel(B))

  1 Comment

Thanks, that looks better than what I had.

Join the 15-year community celebration.

Play games and win prizes!

Learn more
Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

MATLAB Academy

New to MATLAB?

Learn MATLAB today!