MATLAB Answers

Jim Hokanson

Unique rows cell array ignored

Asked by Jim Hokanson
on 1 May 2013

I recently tried to find the unique rows of a cell array and got the following warning:

Warning: The 'rows' input is not supported for cell array inputs.

What was confusing to me was that this option was not supported and yet only a warning was thrown, not an error. After further examination it appears that unique is performed on all elements in the matrix, which is obviously not what I wanted.

Does this seem right? Are there other examples in Matlab where a function ignores an option and then proceeds to do something that is fundamentally different?

Thanks, Jim

  1 Comment

I'll be interested to see what Mathworks people will answer (maybe tomorrow). If I had to place a bet, I'd say that it is for backward compatibility with a "feature" that was a bug but that might have been exploited by people.. who could therefore disable the warning and use a "silent" backward compatibility.

The doc indicates a change in the behavior of UNIQUE and the support for a 'legacy' option. Also, the version of UNIQUE called with cell args is available as an M-file

 C:\Program Files\MATLAB\R2012b\toolbox\matlab\ops\@cell\unique.m

which looks quite experimental/transitional.


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