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Simple Problem Giving Me Trouble

  1. Dec 8, 2009 #1
    I have this question:

    http://img7.imageshack.us/img7/1399/52987960.png [Broken]

    And From this I created this:
    Code (Text):
    delete g286x08.txt; diary g286x08.txt
    clear; clc; close all; echo on
    %
    %Gilat 286/08
    %

    R=8.31;
    M=0.032;
    x=0:20:1000;
    y=70:5:320;
    [X Y]=meshgrid(x,y);

    Z=4*pi*(M./(2*pi*R*Y)).^(3./2)*X.^2.*exp(-M*X.^2)/(2*R*Y);

    surf(X,Y,Z)

    xlabel('Molecules Speed(m/s)'); ylabel('Temperature'); zlabel('Probability')
    %
    echo off; diary off
    And when I run it I get

    Code (Text):
    %
    %Gilat 286/08
    %
    R=8.31;
    M=0.032;
    x=0:20:1000;
    y=70:5:320;
    [X Y]=meshgrid(x,y);

    Z=4*pi*(M./(2*pi*R*Y)).^(3./2)*X.^2.*exp(-M*X.^2)/(2*R*Y);
    Warning: Matrix is singular to working precision.
    > In g286x08 at 13

    surf(X,Y,Z)

    xlabel('Molecules Speed(m/s)'); ylabel('Temperature'); zlabel('Probability')
    %
    echo off; diary off
    And this image
    http://img194.imageshack.us/img194/9489/30221576.jpg [Broken]

    I know there should be something plotted here. Can someone help me?
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Dec 8, 2009 #2
    There is problem in this line:

    Code (Text):

    Z=4*pi*(M./(2*pi*R*Y)).^(3./2)*X.^2.*[B]exp(-M*X.^2)/(2*R*Y)[/B];
     
    it should be: exp((-M * X.^2) ./ (2 * R * Y)

    To avoid mistyping, i think you should disaggregate your eq. (e.g A = 2 * R * Y ; B = (M ./ (pi * A)).^(3/2);). It is easier to debug. :) That is my exp in my sim course.
     
  4. Dec 8, 2009 #3
    Ugh I hate when I do stupid stuff like this. Thank you very much!
     
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