Drawing upside down cone using spherical coordinates.

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Viktor Karlsson
Viktor Karlsson 2021-4-30
评论： Viktor Karlsson 2021-5-3
I wrote the following code:
phi=pi/6;
theta=linspace(0,2*pi,63); %Theta goes from 0 to 2*pi.
a=linspace(0,1,21);
[PHI,THETA,A]=meshgrid(phi,theta,a);
X=A.*sin(PHI).*cos(THETA); % Spherical coordinates
Y=A.*sin(PHI).*sin(THETA);
Z=A.*cos(PHI);
surf(X,Y,Z)
axis equal
It won't draw, but instead gives me an empty 2D graph.
The error message is:
Error using matlab.graphics.chart.primitive.Surface
Value must be a vector or 2D array of numeric type.
Error in surf (line 145)
hh = matlab.graphics.chart.primitive.Surface(allargs{:});

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采纳的回答

Benjamin Kraus
Benjamin Kraus 2021-4-30
The issue you are facing is that when you call meshgrid you are specifying three input vectors, so the output matrices are going to be 3D matrices, but surf only accepts 2D matrices.
My recommendation is to remove phi from the call to meshgrid:
phi=pi/6;
theta=linspace(0,2*pi,63);
a=linspace(0,1,21);
[THETA,A]=meshgrid(theta,a);
X=A.*sin(phi).*cos(THETA);
Y=A.*sin(phi).*sin(THETA);
Z=A.*cos(phi);
surf(X,Y,Z)
axis equal

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