From help-octave-request at bevo dot che dot wisc dot edu Thu Jan 22 16:42:32 2004
Subject: Re: Setting plot ranges
From: "Henry F. Mollet" <mollet at pacbell dot net>
To: Joe Koski <jkoski11 at comcast dot net>,    Octave_post <help-octave@bevo.che.wisc.edu>
Date: Thu, 22 Jan 2004 14:37:34 -0800

Below adjusts x-scale and y-scale in a graph which plots all eigenvalues of
a matrix in the complex plane. I hope it can be adjusted to what you need.
In this example the matrix is a 10x10.
whos
rwd  complex matrix               10      1  la
which came from:
[w,la]=eig(A);
la=diag(la);
imax=find (la==max(real(la)));
% did not work if la1 = la2, had to add "real"
v=conj(inv(w));

Cut several gset commands
axis "square"
% trying rounding up to next 0.1
temp=0.1* ceil (10*la(imax));
axis ([-temp temp -temp temp]);
title ("Eigenvalues in complex plane")
plot (la, "*")
Henry

on 1/22/04 1:35 PM, Joe Koski at jkoski11 at comcast dot net wrote:

> In a recent exercise, because of some extreme "outliers," I needed to
> override the vertical axis of a plot with gset yrange. I had been entering
> this range "manually" e. g., gset yrange [0:10], but the scale varied from
> plot to plot, so I decided to automate the process by calculating a maximum
> that filtered out the extreme values.
> 
> It appears that you can't enter a real (or string) variable such as
> 
> Ymax = 2.0*mean(y);
> S_Ymax = num2str(Ymax);
> 
> into the gset yrange [0:Ymax] or gset yrange [0:S_Ymax] command. Octave just
> tells me that Ymax or S_Ymax are undefined.
> 
> Is there trick to doing this, or must plot ranges be entered only
> numerically, without the use of variable names?
> 
> Thanks for the advice.
> 
> Joe Koski
> 
> 
> 
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Octave is freely available under the terms of the GNU GPL.

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