带有导数和贝塞尔函数的Matlab中的三维球面图

Question

我想在球坐标中绘制以下函数B（r，theta，phi）。

Bo     = 1;
a      = 1;      % m
lambda = 1; % m^-1

syms r theta;

Br = 2*Bo*(a/r)*besselj(1,lambda*r)*cos(theta)
Bth = -Bo*(a/r)*diff(r*besselj(1,lambda*r),r)*sin(theta)
Bph = lambda*a*Bo*besselj(1,lambda*r)*sin(theta)

[Bx,By,Bz]=sph2cart(Bth,Bph,Br);

x=linspace(0,a);
y=linspace(0,a);
z=linspace(0,a);

quiver3(x,y,z,Bx,By,Bz)

当我运行上面的代码时，我收到以下警告和错误。

Warning: Using only the real component of complex data. 
> In getRealData (line 14)
  In quiver3parseargs (line 87)
  In quiver3HGUsingMATLABClasses (line 41)
  In quiver3 (line 41)
  In taylor_state (line 19) 
Error using quiver3 (line 43)
DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use VPA.

Error in taylor_state (line 19)
quiver3(x,y,z,Bx,By,Bz)