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MathGroup Archive 1996

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Re: [Q] Programming & "Not Floating Point Number" Error

  • To: mathgroup at smc.vnet.net
  • Subject: [mg3163] Re: [mg3133] [Q] Programming & "Not Floating Point Number" Error
  • From: penny at edu-suu-scf.sc.suu.edu (Des Penny)
  • Date: Fri, 9 Feb 1996 03:02:28 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

>I have a Mma question that I hope someone out there can help me with.  I
>recently started using Mma for a class and have had a hard time
>"programming" with it. Here is the script/program that i wrote:
>
>--
>epsilon = .01
>gamma = 7
>dt = .125
>stim = 0
>
>y0 = -.5
>w0 = 0.0
>
>For[i=0, i<50, i++,
>f = y0 * (1 - y0 *y0);
>v = y0 + (f - w0) * dt;
>w = w0 +(epsilon*(gamma*y0 - w0)) * dt;
>vee[i] = v;
>doubleu[i] = w;
>y0 = v;
>w0 = w;
>]
>
>ListPlot[{vee,doubleu}]
>---
>
>In the script above I'm essentially calculating a bunch of points
>that I want to plot (V vs. W - I had to use "vee" and "doubleu" to get it
>to work).  The only way I could figure to do it was to store the numbers
>in a list and then use ListPlot[] but I can't get it right.  I keep
>getting:
>
>--
>Graphics::gptn:
>   Coordinate vee in {1, vee} is not a floating-point number.
>Graphics::gptn:
>   Coordinate doubleu in {2, doubleu} is not a floating-point number.
>--
>
>What am I doing wrong?
>
>Thanks for the help,
>
>Noel
*****************************************************************************

Hi Noel:

This is just an addendum to the excellent reply given by Robert Knapp.
Here I show a different way to correct your code:

epsilon = .01;
gamma = 7;
dt = .125;
stim = 0;

y0 = -.5;
w0 = 0.0;

points={};

For[i=0, i<50, i++,
f = y0 * (1 - y0 *y0);
v = y0 + (f - w0) * dt;
w = w0 +(epsilon*(gamma*y0 - w0)) * dt;
AppendTo[points, {v,w}];
y0 = v;
w0 = w;
]

ListPlot[points];

Cheers,

Des Penny


==========================
Des Penny
Physical Science Dept.
Southern Utah University
Cedar City, UT 84720

VOICE: (Office): (801) 586-7708
       (Home)  : (801) 586-2286
FAX:    (801) 865-8051
e-mail: penny at suu.edu
==========================



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