Re: setdiff: Octave <-> Matlab

[Henry F. Mollet]

I doubt that setdiff(A,B) can detect similarity between 2 matrices. It
simply checks matrix elements in A and B.

Presumably, the 'rows' option would produce
ans =

  1
  1
  1
in the *example below*. However, my octave-forge setdiff.m must be an old
version and cannot handle the 'row' argument.
Henry

A =

  1  1  1
  1  1  1
  1  1  1

octave:30> B
B =

  2  2  2
  2  2  2
  2  2  2

octave:31> setdiff(A,B)
ans =   1 % 1 in matrix A does not appear in matrix B

octave:32> setdiff(A,B,'rows')
usage: setdiff(a,b)
error: evaluating if command near line 28, column 3
error: called from `setdiff' in file
`/Users/mollet/Desktop/usr/local/share/octave/2.1.55/site/m/octave-forge/set
/setdiff.m'

Another example:
octave:32> A= [1 2 3;4 5 6;7 8 9]
A =

  1  2  3
  4  5  6
  7  8  9

octave:33> B=A+10
B =

  11  12  13
  14  15  16
  17  18  19

octave:34> setdiff(A,B)
ans =

  1
  2
  3
  4
  5
  6
  7
  8
  9

octave:35> setdiff(A,B,'rows')
usage: setdiff(a,b)
error: evaluating if command near line 28, column 3
error: called from `setdiff' in file
`/Users/mollet/Desktop/usr/local/share/octave/2.1.55/site/m/octave-forge/set
/setdiff.m'
octave:35> 






on 6/14/05 5:54 PM, Louis Ciotti at address@hidden wrote:

> Mike Miller wrote:
> 
>> On Tue, 14 Jun 2005, John W. Eaton wrote:
>> 
>>> On 14-Jun-2005, address@hidden wrote:
>>> 
>>> | I am tying to use the setdiff command in octave.  I am trying to get a
>>> | script that works in Matlab to work in octave.  In matlab the syntax
>>> | is:
>>> |
>>> | 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.
>>> |
>>> | in octave the syntax is similar, but it does not take the rows
>>> | option.  Not knowing exactly how Matlab works(I do not have a working
>>> | copy) I do not know how to get they same output in octave.  Can
>>> | someone help who has a copy of Matlab??
>>> 
>>> Why should that be necessary?  If you want to implement something for
>>> Octave, then you must not refer to Matlab M-files.  You know what the
>>> function is supposed to do, so the task is to make an independent
>>> implementation.
>> 
>> 
>> I think he does not know what the function is supposed to do because
>> he doesn't understand the 'rows' argument.
>> 
>> Sometimes a simple google search can help because MATLAB docs are on
>> the web:
>> 
>> http://taxa.epi.umn.edu/bgnews/2003/msg00074.html
>> 
>> c = setdiff(A, B)  returns the values in A that are not in B. The
>> resulting vector is sorted in ascending order. In set theory terms, c
>> = A - B. A and B can be cell arrays of strings.
>> 
>> 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.
>> 
>> Mike
>> 
> 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...
> 
> 
> 
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