strange quiver3 plot

Hello there!

I'm having throuble with a quiver plot. There's this M vector field I want to display over this curved ribbon callend by plotaFita( ) in the code bellow. All vectors should look the same size but it looks a lot bigger in the curve maximum. Any ideias? It's funny because when I put the zero in quiver scale I do got a field with constant norm, but it's completly different, with the arrows all over the origin of the plot.

  Omega = @(theta) 2*atan( exp( (theta-theta0)/delta ) );

  Mr = @(theta) Ms*sin(fi).*sin(Omega(theta));
  Mtheta = @(theta) Ms*cos(Omega(theta));
  Mz = @(theta) Ms*cos(fi).*sin(Omega(theta));


  Mx = @(theta) Mr(theta).*cos(theta) - Mtheta(theta).*sin(theta) ;
  My = @(theta) Mr(theta).*sin(theta) + Mtheta(theta).*cos(theta) ;

  XYZ = plotaFita(dr,dz,Raio,Nx,Nz); hold on;
  [n,m] = size(XYZ);
  X = XYZ(:,1:(m/3)); Y = XYZ(:,(m/3 + 1):(2*m/3)); Z = XYZ(:,(2*m/3+1):end);

  Theta = atan(Y./X);

  quiver3(X,Y,Z,Mx(Theta),My(Theta),Mz(Theta));
  %quiver3(X,Y,Z,Mx(Theta),My(Theta),Mz(Theta),0);  

[KSSV]

We cannot run your code as the function: plotaFita is not given here. One suggestion is replace atan with atan2.

[Gabriel Silva]

I'm attaching here this function so you can do it.

[Gabriel Silva]

Do anyone else got any other ideia?

[KSSV]

It is not a complete code. How you expect us to run?

XYZ = plotaFita(dr,dz,Raio,Nx,Nz); hold on;

dr, dz, Raio, Nx, Nz not defined. Okay, we can go ahead with some values. But how about variables in the below lines?

Omega = @(theta) 2*atan( exp( (theta-theta0)/delta ) );
Mr = @(theta) Ms*sin(fi).*sin(Omega(theta));
Mtheta = @(theta) Ms*cos(Omega(theta));
Mz = @(theta) Ms*cos(fi).*sin(Omega(theta));

[Gabriel Silva]

Oh, sorry, I forgot about these values.

I use:

dr = 2e-06 ; dz = 1.8e-6; Raio = 3.1831e-05; Nx = 15; Nz = 10;

and

theta0 = pi/2; delta = 1.0504e-06; Ms = 813 ; fi = pi/2

[Gabriel Silva]

Do you think you can run now, KSSV?