From help-octave-request at che dot utexas dot edu  Wed Jan 18 10:35:22 1995
Subject: I and J variables
From: Eyal Doron <doron at mickey dot mpi-hd dot mpg dot de>
To: help-octave at che dot utexas dot edu (Octave mailing list)
Date: Wed, 18 Jan 1995 17:35:12 +0100 (MET)

Hi,
   I know its a feature, but IMHO its an irritating one. I and J are
defined as sqrt(-1), like i and j, except that they are read-only
and can't be changed. This is playing havoc with some of my MATLAB
functions, which usually use I as an index vector and J as a bessel
function vector. I know its trivial to fix my files, but its
bothersome nevertheless. Is there any way to remove this feature?

BTW, I've just transferred a bessel function .m file from Matlab to
Octave 1.1.0. I needed to change the I variable name, and I also
got the warning: "warning: empty matrix found in matrix list" on
the lines
     Ii=find(z); LI=length(Ii);
     Jn(:,Ii)=[ones(1,LI);zeros(n,LI)];
when "z" contained only zeros. It seemed to work OK, though. I think
these warnings are superfluous, since empty matrices are not an error
but a natural part of the language. Again, solved by enclosing the
whole thing in an "if any(z)==1,...,end" block, which is however not
necessary in Matlab. Nevertheless, I'm impressed.

Bye,
   Eyal Doron