From help-request at octave dot org Tue Jan 25 10:08:23 2005
Subject: Cell array membership (was: Iterating over cell arrays)
From: Hamish Allan <hamish at jamkit dot com>
To: help at octave dot org
Date: Tue, 25 Jan 2005 16:11:30 +0000

Since I posted this, a friend of mine has told me that Matlab 7 works 
in the way I would expect. Is it therefore reasonable to make this a 
feature request for Octave?

In the meantime, here is the hack I used in case anyone else wants to 
do this (please post better solutions though!):

%%%%

function t = iscellarraymember(item, arr)
     for i=1:length(arr)
         t = equal(item, arr{i});
         if t
             break;
         end
     end
end

function t = equal(m1, m2)
     t = 0;
     try
         if (size(m1) == size(m2));
             t = (m1 == m2);
         end
     catch
     end
end

%%%%

Cheers,
Hamish

On Jan 25, 2005, at 2:06, Hamish Allan wrote:

> Hi,
>
> I'd like to be able to check for membership in a cell array, e.g.:
>
> octave> cell_array = { 'Foo' 'Bar' 'Baz' 'FooBar' };
> octave> ismember('Bar', cell_array)
>
> ans =
>  1 1 1
>
> octave> ismember('FooBar', cell_array)
>
> ans =
>  1 1 1 1 1 1
>
> octave> ismember('z', cell_array) % NB if cell_array were a character 
> matrix this would return 'ans = 1'
>
> ans = 0
>
> But of course I get:
>
> error: binary operator `==' not implemented for `cell' by `cell' 
> operations
> error: evaluating binary operator `==' near line 67, column 24
> [etc.]
>
> Because there is no guarantee that cell matrices will be comparable, 
> none are compared.
>
> Two queries:
>
> 1) Would it be reasonable for ismember() to be designed to behave in 
> the way I describe above?
> 2) Is there a simpler way to do what I want to do than writing a 
> function to iterate over the members of cell_array? I don't even need 
> the intersection, I just want a true or false test for membership.
>
> Many thanks,
> Hamish



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------