From help-request at octave dot org Wed Jan 11 12:41:29 2006
Subject: Re: function file question and plot using polar coordinates
From: Shai Ayal <shaia at biocontrol dot co dot il>
To: "Tetsuji \"Maverick\" Rai" <maverick31337 at gmail dot com>
Cc: help at octave dot org
Date: Wed, 11 Jan 2006 20:31:03 +0200

Tetsuji "Maverick" Rai wrote:
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> Two newbie questions in one email :)  Because the online document (and
> written document) doesn't help me in this part....
> 
> #1. I am trying to write a function file, but octave complains loading
> the function file; e.g. I made a file of sombrero2(n) like (just copied
> "type sombrero")
> - ----------sombrero2.oct--------------
> function sombrero2 (n)
> 
>   if (nargin != 1)
>     usage ("sombrero (n)");
>   endif
> 
>   if (n > 1)
>     x = y = linspace (-8, 8, n)';
>     [xx, yy] = meshgrid (x, y);
>     r = sqrt (xx .^ 2 + yy .^ 2) + eps;
>     z = sin (r) ./ r;
> 
>     mesh (x, y, z);
>   else
>     error ("sombrero: number of grid lines must be greater than 1");
>   endif
> 
> endfunction
> - ----------------
> 
> and tried "load sombrero2.oct", but octave says:
> 
> octave:4> load "sombrero2.oct"
> error: load: sombrero2.oct: inconsistent number of columns near line 2
> error: load: unable to extract matrix size from file `sombrero2.oct'
> 
> and denies.   However if I copy&paste this function in octave's
> commandline prompt, sombrero2(n) works normally.  What's the difference
> and how can I make octave read it?   octave's document isn't clear on
> this to me...or am I missing anything?

The way to do this is to save it as sombrero.m and than just type

sombrero

at the command line. what you did, "load sombrero.oct" tries to load 
this file into a matrix as if it were a sequence of numbers.


> #2
> I'm trying to plot sombrero-like graphics using polar coordinates in
> x,y.  i.e. x=r*sin(theta); y = r*cos(theta); and z = (function of r and
> theta); (it may look like x and y are reverse, but in my case it's
> correct.)   I tried to define the ranges of r and theta, but it won't
> work as expected.  It looks like 3 dimension graphics accepts only
> lattice points of (x,y).  Then must I calculate r and theta from x,y?
> It's a bit inconvenient..... but it's not so difficult and if there are
> no other ways, I'll do so.
> 

I'm not sure about this one


> Thanks in advance!
> 
> - -Tetsuji
> - --
> Tetsuji 'Maverick' Rai
> main page http://maverick6664.bravehost.com/
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