setdiff output differs from matlab

[David Bateman]

soren at hauberg.org wrote:
> Quoting "John W. Eaton" <jwe at bevo.che.wisc.edu>:
>   
>> On  9-Sep-2008, Søren Hauberg wrote:
>>
>> | tir, 09 09 2008 kl. 13:07 -0500, skrev Michael Ferris:
>> | > In octave: x = 1:5; y = setdiff(x,x); size(y)
>> | > ans =
>> | >
>> | >      0     0
>> | >
>> | > In matlab: x = 1:5; y = setdiff(x,x); size(y)
>> | > ans =
>> | >
>> | >      1     0
>> |
>> | Both produce empty matrices, it's only their size that differs.
>>
>> Yes, but if it makes sense to do so, I think we should try to make the
>> sizes the same.
>>     
>
> I agree. I was just pointing out the subtlety of the bug.
>
>   
>> What does Matlab return for each fo the following,
>> and does it make sense, or does it just seem like an accident of the
>> implementation, when it could just as easily return [] in all cases?
>>     
>
> In Matlab 7.6.0.324 (R2008a) I get
>
>   
>>> x = 1:5;
>>>
>>>   setdiff (x, x)
>>>       
>
> ans =
>
>     Empty matrix: 1-by-0
>
>   
>>>   setdiff (x', x)
>>>       
>
> ans =
>
>     Empty matrix: 1-by-0
>
>   
>>>   setdiff (x, x')
>>>       
>
> ans =
>
>     Empty matrix: 1-by-0
>
>   
>>>   setdiff (x', x')
>>>       
>
> ans =
>
>     Empty matrix: 0-by-1
>
>
> Søren
>
>
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>
>   
So if the args are both vectors, but different orientations then Matlab 
converts them both to be row vectors.

D.


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