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Why is my MATLAB plot wrong?

Asked by Edward Lisa on 18 May 2018
Latest activity Edited by KALYAN ACHARJYA on 21 May 2018

Hi! I just started my Matlab course and i have run into a little problem which i hope you can help me with. I am suppose to write a function which integrates a function e^(-t^2) from 0 to some x which is a variable in the function. I did that like this:

 function y = simpson_method(x)
 y1 = exp(-0.^2);
 y2 = exp(-(x).^2);
 c = 0;
 d = 0;
 incr = 0.1;
 for i = 1 : (x - 0)/incr - 0.5
    y = exp(-(0 + i*incr).^2);
    if i/2 == floor(i/2)
        d = d + y;
        continue
    else
        c = c + y;
        continue
    end
end
 y = incr/3 * (y1 + 4*c + 2*d + y2);

The function integrates correctly and gives me a desired output for every x. But the problem is when i try to plot it:

 x = 0:0.1:15;
 y = simpson_method(x);
 plot(x,y)

It gives me the wrong graph which i find weird because all the outputs are correct. I get this which is nonsense. Whats happening?

  5 Comments

@Edward Lisa: can you please confirm the ambiguous syntax:

  1. e^((-t)^2)
  2. e^(-(t^2))

Its e^(-(t^2))

If your y values are correct I can see no reason at all why plot would not give the correct answer so your y values cannot be correct if you are literally just calling plot.

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1 Answer

Answer by KALYAN ACHARJYA on 21 May 2018
Edited by KALYAN ACHARJYA on 21 May 2018

Shown Graph the x ranges are different

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