How to plot equations with complex parts?

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Marco Froelich 2017-7-6

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https://ww2.mathworks.cn/matlabcentral/answers/347568-how-to-plot-equations-with-complex-parts

评论： KSSV 2017-7-6

I would like to plot the equation for a sphere, in which I had to reorganise to:

Z = sqrt(1 - X^2 - Y^2)

However I get a error saying my equation cannot be complex. How do I get around this?

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Answer 1

KSSV 2017-7-6

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https://ww2.mathworks.cn/matlabcentral/answers/347568-how-to-plot-equations-with-complex-parts#answer_273060

在 MATLAB Online 中打开

You can use parametric form of equations of sphere and plot it as shown below:

Radius = 1 ;
Height = 1 ;
M = 50 ;
N = 50 ;
% Discretizing the theta and phi of the shell
nT = -linspace(0,2*pi,M+1) ;
nP = linspace(0,pi,N+1) ;
[T, P] = meshgrid(nT,nP) ;
% Convert grid to cartesian coordintes
X = Radius.*cos(T).*cos(P);
Y = Radius.*cos(T).*sin(P);
Z = Height*Radius.*sin(T) ;
%
surf(X,Y,Z)

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Marco Froelich 2017-7-6

Yes I have seen this on other question/answers. But it is time consuming, and I have manyyyy spheres to plot. I was wondering if there was another way? It is quite dumb of Matlab not to recognize something such as:

x^2 + y^2 + z^2 = 1