matrix subsetting

[John W. Eaton]

On 30-Mar-2000, Heber Farnsworth <address@hidden> wrote:

| How does one do matrix subsetting in a dynamically loaded function (.oct
| file)?  I know how to put a whole matrix into a certain place in a
| larger matrix using insert but I don't know how to do the reverse.  I
| want to create a matrix out of part of an existing matrix.  In an m-file
| you would write
| 
| Y = X(a:b,c:d);
| 
| Does anyone know how to do this?

Yes, but exactly how depends on what kinds of objects X, a, b, c, and
d are.  If you have X as a Matrix object, and a, b, c, d are ints, you
can use

  Matrix Matrix::extract (int r1, int c1, int r2, int c2) const;

(you'll need to adjust for the fact that Matrix objects use a 0-based
indexing).

jwe



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