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Need help with 3D surface plot of complex function

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Joshua
Joshua 2014-4-10
评论： José Peralta 2020-4-30
I'm pretty sure I understand how to code this, the way the instructions are worded for it are confusing me. Here's a screenshot of them: http://i.imgur.com/Y6Rw8y6.png
So I understand I would simply make two vectors for the ranges of sigma and omega.
sig = -8:0.1:0;
omeg = -10:0.1:10;
Then the meshgrid
[X,Y] = meshgrid(sig, omeg);
Not quite sure how to create a vector for parts of the complex variable, a grid for s, or how to determine the magnitude of the function since it asks you to plot the real and imaginary components. I understand the real is sigma and the imaginary is omega, but then why does it add I may need to use the real and imag commands? The only surface plots I've done have been simple where you're given a range of two variables, you simply create the meshgrid, then evaluate the function using the meshgrid and save that as z, then plot it with the surf command. Also how come wn = 5 but then I'm given a range separately as well?
EDIT: This is what I have right now:
sigma = -8:0.1:0;
omega = -10:0.1:10;
[x,y] = meshgrid(sigma, omega);
s = x + y;
z = (5^2)./(s.^2 + 2*0.4*5.*s + 5^2);
surf(x,y,z);

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回答（2 个）

Max Peterson
Max Peterson 2015-5-17
Try this one:
[x,y] = meshgrid(-3 : 0.05: 3);
s = x + i*y;
z=abs((5^2)./(s.^2 + 2*0.4*5.*s + 5^2));
figure;
surf(x, y, z)
  1 个评论
José Peralta
José Peralta 2020-4-30
Hola buenas tardes. Podrías recomendarme bibliografía o ejemplos de gráficas de funciones de Variable Compleja. Muchas gracias.

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Marta Salas
Marta Salas 2014-4-10
编辑：Marta Salas 2014-4-10
s is a complex number and so it's F(s) (z in your code). This is why the problem ask you to plot the magnitude of F(s) which is the absolute value of F(s)
s = x + i*y;
z = (5^2)./(s.^2 + 2*0.4*5.*s + 5^2);
magnitude = abs(z);
surf(x,y,magnitude);
  1 个评论
Max Peterson
Max Peterson 2015-5-17
It doesn't work. I get following error message:
"Error using surf (line 57)
Z must be a matrix, not a scalar or vector."

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