Problems with line plots

Hi there,

can someone please tell me why my program outputs such a line?

it should look like this:

This is my code:

   [u,v] = meshgrid(linspace(-2.5,2.5,40),linspace(-2.5,2.5,40));
    x = u-(u.^3/3)+u.*v.^2;
    y = -v+(v.^3/3)-v.*u.^2;
    z = u.^2-v.^2;
    mesh(x,y,z)
    hold on
    axis equal;
    [t,X] = ode45(@Enneper,[0,4*pi],[0,.1,0,.1]);
    u = X(:,1);
    v = X(:,3);
    x = u-(u.^3/3)+u.*v.^2;
    y = -v+(v.^3/3)-v.*u.^2;
    z = u.^2-v.^2;
    plot3(x,y,z,'color','r','LineWidth',1);  
function xprime = Enneper(t,x)
    xprime = zeros(4,1);
    xprime(1) = x(2);
    xprime(2) = (2.*x(1).*x(4).^2)/(x(1).^2+x(3).^2+1)-(2.*x(1).*x(2).^2)/(x(1).^2+x(3).^2+1)-(4.*x(3).*x(2).*x(4))/(x(1).^2+x(3).^2+1);
    xprime(3) = x(4);
    xprime(4) = (2.*x(3).*x(2).^2)/(x(1).^2+x(3).^2+1)-(2.*x(3).*x(4).^2)/(x(1).^2+x(3).^2+1)-(4.*x(1).*x(2).*x(4))/(x(1).^2+x(3).^2+1);
end  

Thanks!

Answer 1

[Cris LaPierre]

You create that line with your plot3 command. If it should be doing what is shown in your other images, you may need to check your equations for x, y, and z.

[cheb]

Hi, thank you for your answer. The equations for x, y, z are all correct

[Cris LaPierre]

Some quick googling suggests that the lines you desire are created by setting u and v equal to zero.

●

[cheb]

I also found and tried that, but then I get unfortunately an error message in my code

[Cris LaPierre]

Worked for me. The image I created is in my post above.

[cheb]

really? can you maybe show me where exactly you defined that? I have only started programming a few weeks ago and probably defined it in the wrong place

[Cris LaPierre]

I'll get you started.

1. Find your equations for x,y and z at the bottom of your code.
2. Change all the u's to 0.
3. Run your code.

[cheb]

I'm trying that out now. Are the equation for x,y and z at the bottom:

, , ?

[cheb]

Sorry, i don't get it. Can you please show me, how you did that?

[Cris LaPierre]

I suggest you reread items 1-3. I answer your questions there.