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Re: something like a modulo function (but not)?
From: |
E. Joshua Rigler |
Subject: |
Re: something like a modulo function (but not)? |
Date: |
Wed, 27 Oct 2004 11:37:02 -0600 |
Yes, this is perfect. Thanks!
-EJR
On Wed, 2004-10-27 at 11:28, Robert A. Macy wrote:
> does
> mod(idx1-1,5)+1
> work?
>
> On Wed, 27 Oct 2004 11:15:09 -0600
> "E. Joshua Rigler" <address@hidden> wrote:
> > I feel a little silly even asking this question, but
> > since when has that
> > stopped me :^)? I have a vector of sequential indices to
> > a 2-D matrix
> > that I want to convert to a set of column-wise vector
> > indices. For
> > example a particular 5x5 matrix would be fortran indexed
> > as:
> >
> > mtrx = [ 1 6 11 16 21 ]
> > [ 2 7 12 17 22 ]
> > [ 3 8 13 18 23 ]
> > [ 4 9 14 19 24 ]
> > [ 5 10 15 20 25 ]
> >
> > I extract a subset of this matrix that gives me the
> > following vector of
> > indices:
> >
> > idx1 = [ 3 5 8 10 13 15 18 20 23 25 ]
> >
> > and wish to convert it to something like:
> >
> > idx2 = [ 3 5 3 5 3 5 3 5 3 5
> > ]
> >
> > The first thing that popped into my head was that I would
> > need to use
> > the modulo function in Octave (i.e., idx2=mod(idx1,5)),
> > but of course
> > that would give me:
> >
> > idx2 = [ 3 0 3 0 3 0 3 0 3 0
> > ]
> >
> > I guess what I really want is something similar to
> > modulo, except where
> > mod(n,I*n)=n, not zero ("I" is an integer). The best
> > solution I could
> > come up with on my own is:
> >
> > octave:44> idx2 = mod(idx1,5)+(mod(idx1,5)==0)*5
> > idx2 =
> >
> > 3 5 3 5 3 5 3 5 3 5
> >
> > Can anyone out there suggest something a little more
> > elegant that would
> > have less impact on a long and already computationally
> > intensive
> > iterative function? Am I just being dense?
> >
> > -EJR
> >
> >
> >
> >
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> > Octave is freely available under the terms of the GNU
> > GPL.
> >
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> > http://www.octave.org/archive.html
> >
> -------------------------------------------------------------
> >
>
>
>
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
>
> Octave's home on the web: http://www.octave.org
> How to fund new projects: http://www.octave.org/funding.html
> Subscription information: http://www.octave.org/archive.html
> -------------------------------------------------------------
-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.
Octave's home on the web: http://www.octave.org
How to fund new projects: http://www.octave.org/funding.html
Subscription information: http://www.octave.org/archive.html
-------------------------------------------------------------