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# Re: array indices again

• Subject: Re: array indices again
• From: Martin Schultz <mgs(at)io.harvard.edu>
• Date: Thu, 03 Jun 1999 23:22:42 -0400
• Newsgroups: comp.lang.idl-pvwave
• Organization: Harvard University
• References: <3756B9EC.D05637F9@rosella.llnl.gov>
• Xref: news.doit.wisc.edu comp.lang.idl-pvwave:15046

```Henry Chapman wrote:
>
> Hi all,
>
> I remember a few weeks back there was a lot of discussion about indexing
> multiple dimensions of arrays, [...]

> It seems that by extending the 2-d array a into another dimension, where
> the extra dimension has no size (sounds like string theory!) the
> indexing works the way I want it to.  I noticed this when I had a 3-d
> array and was extracting a 2-d array from it, as in b[x, x, i] where x
> is a 1-d array and i is a scalar.  This seems to work on arrays of any
> dimension.
>
> I apologise if this was mentioned before,
>
> Henry.
>
> --
> Henry Chapman                          mailto:chapman9@llnl.gov
> Information Science & Technology Program
> Lawrence Livermore National Lab
> L-395, 7000 East Ave., Livermore CA 94550

Henry,

nice feature! I was really astonished when I saw it works even for
non-equal dimensions:
a = findgen(20,10)
x = indgen(10)*2
y = indgen(5)*2
print,a[x,y,0]

however, (a puzzle for the unexperienced IDL user):
print,a[x,y]
will result in an error message...

Martin.

--

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Martin Schultz, DEAS, Harvard University, 29 Oxford St., Pierce 109,
Cambridge, MA 02138          phone (617) 496 8318   fax (617) 495 4551
e-mail mgs@io.harvard.edu    web http://www-as/people/staff/mgs/

```