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MATLAB Help

  1. Oct 17, 2005 #1
    Maybe not the proper place to post... but it seems like physics forums is going through some type of "crazy" change right now. Anyways... I'm having trouble finding a website with directions on how to plot a system of equations in MATLAB. If anyone has a basic M-file they could show me, or a tutorial... that'd be really awesome! Thanks for the help :)
     
  2. jcsd
  3. Oct 17, 2005 #2

    enigma

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    Code (Text):


    x=[-5:.1:5]; % x is a vector containing the numbers -5, -4.9, -4.8, ..., 4.9, 5. Semicolon means don't display to screen
    y=4x.^3 - 2x.^2 - 12; % The '.'^ raises each element of the vector to the power listed.
                                    % If you just did ^ it would do matrix multiplication which doesn't work unless the matrix is square.

    plot(x,y,'r*') % Plot variable X on the horizontal axis, y on the vertical, and display the points as red stars
     
    Is that what you wanted, or did you need something more?
     
  4. Oct 17, 2005 #3
    Actually, I already knew about the plot command. What I didn't know is that you can plot multiple equations with it.

    t1=0:.1:10;
    t2=10:.1:20;
    y1=t1.*1;
    y2=t2./t1;

    plot(t1,y1,'r-',t2,y2,'r2-',...

    But thanks for the reply :smile:
     
  5. Oct 17, 2005 #4

    enigma

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    Ah, ok.

    You can also skip the 'xxx' and have it automatically assign the colors.

    Another way to do it is to hold the plot like so:

    Code (Text):

    figure(1)

    plot(x1,y1)

    hold on

    plot(x2,y2)
    plot(x3,y3)

    hold off
     
    You can also simply type 'hold' to toggle it.
     
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