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## Re: Excluding elements of a matrix

 From: antonio palestrini Subject: Re: Excluding elements of a matrix Date: Wed, 20 Dec 2006 00:47:13 +0100

```2006/12/19, Joseph Wakeling <address@hidden>:
```
```Thanks to all for useful replies.

How feasible would it be to implement a simple syntax for something like
this in a future version of Octave, along the lines of,

a(\6)   [i.e. a excluding element 6]

A(:,\[5 7])    [matrix A excluding columns 5 and 7]

... inspired by set notation?
```
```
If you have to work with this kind of data manipulations the best
thing to do, in my opinion, is to write a function like the following
for the matrix example (the vector one may be constructed analogously)

function B = del_columns(A,q)
# use: function B = del_columns(A,q)
#
# The function deletes the A columns specified in the vector q
B = A;
B(:,q) = [];
endfunction

example:
[oct 3] A=rand(6,4)
A =

0.95370  0.53598  0.85039  0.25881
0.63536  0.41243  0.13631  0.54626
0.25284  0.09450  0.43455  0.19440
0.97259  0.45803  0.66549  0.42452
0.57042  0.45608  0.69860  0.59288
0.95337  0.11660  0.39163  0.34055

[oct 4] q = [2 4]
q =

2        4

[oct 5]  B = del_columns (A,q)
B =

0.95370  0.85039
0.63536  0.13631
0.25284  0.43455
0.97259  0.66549
0.57042  0.69860
0.95337  0.39163

ciao
antonio

--
Prof. Antonio Palestrini
DSGSS - University of Teramo, Italy