Input arguments for the cross function

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John Draper
John Draper 2016-1-18
评论： John Draper 2016-1-20
Hi, I'm trying to use the cross function to give me the cross product of two sets of vectors at points on the surface of the sphere.
I keep getting the error "A and B must have at least one dimension of length 3". I'm not entirely sure what this means and what I should do to my data to correct it?
I have checked using 'whos' and both my A and B are of the 'double' data type.
Here is my code:
if true
R=22; phi=linspace(0,pi,50); theta=linspace(pi/2,pi/2,50);
[phi,theta]=meshgrid(phi,theta);
X=R*sin(phi).*cos(theta); Y=R*sin(phi).*sin(theta); Z=R*cos(phi);
con=50; T=Z./R;
U=3*con.*X.*Z./R.^5 %mag field in x
V=3*con.*Y.*Z./R.^5; %mag field in y
W=con.*((3*Z.^2 -(R.^2)))./R.^5;
hold
dx=gradient(X); dy=gradient(Y); dz=gradient(Z)
A=U.*dx; B=V.*dy; C=W.*dz;
k=A+B+C;
k1=k./sqrt(dx.*dx +dy.*dy + dz.*dz);
projx=k1.*dx; projy=k1.*dy; projz=k1.*dz;
%figure
%quiver3(X,Y,Z,projx,projy,projz,'color',[0,0,0])
proj=[projx projy projz];
[Nx,Ny,Nz]=surfnorm(X,Y,Z);
N=[Nx Ny Nz];
j1=cross(N,proj);
% code
end
also I'm assuming that if I wanted the components of the resulting cross product vector individually i would code:
if true
j1x=cross(N,proj,1)
j1y=cross(N,proj,2)
j1z=cross(N,proj,3)
% code
end
Thanks in advance for your help
  1 个评论
John Draper
John Draper 2016-1-20
Managed to do this by:
if true
[Nx,Ny,Nz]=surfnorm(X,Y,Z);
N=[Nx,Ny,Nz];
d=[dx,dy,dz];
i=(Ny.*dz - Nz.*dy);
j=(Nz.*dx - Nx.*dz);
k=(Nx.*dy - Ny.*dx);
% code
As this was in the required direction. end

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