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Colon inconsistency between Matlab and Octave

From: Arno Peters
Subject: Colon inconsistency between Matlab and Octave
Date: Thu, 28 Jan 1999 01:28:51 +0100 (CET)


1) In Matlab, the colon operator _always_ returns a column vector.

2) pause flushes buffers in Matlab, not in Octave

Verified with Octave version 2.1.10 and 2.0.13.

Case 1:

octave> a = [1 2; 3 4];
octave> a(:)
ans =


Case 2:

octave> b = [1; 2; 3; 4];
octave> b(:)
ans =


Case 3:

octave> c = [1 2 3 4];
octave> c(:)
ans =

  1  2  3  4

Cases 1 and 2 are consistent with Matlab but for case 3 the results
should be identical to case 2.  I guess I would expect this also from
looking at the behaviour of the colon operator on matrixes.

Currently I am unable to verify with Matlab but I have seen at least
one script that relies on this feature: robot, a set of scripts in the
contributed directory of the Matlab site.  The Robot Toolbox homepage
is at

Contrary what the author claims in the documentation, the demo runs
perfectly except for this minor incompatibility.  BTW, he used Matlab
version 4 and Octave version 1.1.1.  Things have changed considerably
since then (1996).

At least options 2 and 3 of 'rtdemo' will bomb out after you hit one
or more keys.  This way, I also found out that apparently 'pause' will
flush the buffers in Matlab.  When you run the other demos will also
make this clear because in Octave you don't see a thing until you hit
a key or several keys.

Thanks for any feedback you can provide.

Arno Peters

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