Re: setdiff: Octave <-> Matlab

[Mike Miller]

On Tue, 14 Jun 2005, Louis Ciotti wrote:

> > c = setdiff(A, B, 'rows'), when A and B are matrices with the same number 
> > of columns, returns the rows from A that are not in B.
>
> Exactly... I do not see what the 'rows' option does.  For example say I 
> have to similar matrices A and B with 3 columns of 150 values.  With 
> setdiff(A,B,'rows') is the result a 3 column matrix with each column 
> contain the values from the rows A that were not in the rows of B???
>
> Like I said this would be easy if I had MATLAB to check it...

I'm sorry.  Rereading this I see that I sent you something you already 
had!  That wasn't much help.  I hope the stuff below helps more.  It is 
from MATLAB.  It looks like it does what you suggested in your question 
above.  Strangely though, at least in this example, the rows are returned 
in the reverse order.

Mike


> > X=ceil(10*rand(4))

X =

    10     9     9    10
     3     8     5     8
     7     5     7     2
     5     1     8     5

> > Y=ceil(10*rand(4))

Y =

    10     1     2     3
    10     4     3     2
     5     9     2     1
     9     1     7     8

> > Y(3,:)=X(2,:)

Y =

    10     1     2     3
    10     4     3     2
     3     8     5     8
     9     1     7     8

> > setdiff(X,Y)
??? Error using ==> setdiff
A and B must be vectors or 'rows' must be specified.

> > setdiff(X,Y,'rows')

ans =

     5     1     8     5
     7     5     7     2
    10     9     9    10



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