quiver3 using 3D spherical coordinates?

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John Draper
John Draper 2016-1-5
评论： Bin Jiang 2023-3-2
Hi, I've read a lot of posts on this site about using quiver3 to plot a function in non-rectangular coordinates and I am still a little bit confused.
Here is my attempt to plot a 3D function in spherical coordinates using quiver3
if true
[r,theta,phi] = meshgrid(0:0.1:100,-pi/2:pi/100:pi/2, 0:pi/100:pi); %defines meshgrid coverage
%r=(X.^2+Y.^2+Z.^2).^0.5 ;
const=1; %mu_0 * M_4 / 4*pi
Br= const*2*cos(theta)./(r.^3); %mag field in rho
Btheta= const*sin(theta)./(r.^3);%mag field in theta
Bphi=0;
%magnetic field function
figure
quiver3(r,theta,phi,Br,Btheta,Bphi,5)% no defines arrow length, other define direction
%defines arrow direction (u,v,w) at point (x,y,z)
hold on
%surf(X,Y,Z) %produces surface
axis equal %defines axis parameters
hold off
% code
end
This didn't seem to work (I got an error saying V and W need to be the same size). So I tried converting to rectangular before using the quiver function.
if true
[r,theta,phi] = meshgrid(0:0.1:100,-pi/2:pi/100:pi/2, 0:pi/100:pi); %defines meshgrid coverage
%r=(X.^2+Y.^2+Z.^2).^0.5 ;
const=1; %mu_0 * M_4 / 4*pi
U= const*2*cos(theta)./(r.^3); %mag field in rho
V= const*sin(theta)./(r.^3);%mag field in theta
W=0;
%magnetic field function
r=(X.^2+Y.^2+Z.^2).^0.5 ;
X=r.*sin(phi).*cos(theta);
Y=r.*sin(phi).*sin(theta);
Z=r.*cos(phi);
figure
quiver3(X,Y,Z,U,V,W,5)% no defines arrow length, other define direction
%defines arrow direction (u,v,w) at point (x,y,z)
hold on
%surf(X,Y,Z) %produces surface
axis equal %defines axis parameters
hold off
% code
end
Which doesn't seem to work either. Is it not possible to use spherical coordinate in quiver or am I doing something wrong?
Thanks, John
  2 个评论
John Draper
John Draper 2016-1-5
After doing some more reading, I think I realise the answer to my question is no. It is better to convert back into Cartesian and then use the quiver3 function.
Bin Jiang
Bin Jiang 2023-3-2
It seems that you only specified one element to W, while it should be something like sz=size(U); W= zeros(sz). Perhaps, there is a better way!

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