How to draw this 3D plot (PSD cone)

Question

Dian-Jing 2015-1-7

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/169232-how-to-draw-this-3d-plot-psd-cone

回答： Stefan Reich 2016-7-29

采纳的回答： Stefan Reich

在 MATLAB Online 中打开

Hi all:

I have vectors: x,y,z with the same dimension.

I use plot(x,y,z,',') to plot it. The following is the code:

clear all;                   
close all;
clc
num = 0;
%%loop
for x = 0 : .02 : 1
  for y = -1 : .02 : 1
      for z = 0 : .02 : 1
          num = num + 1;
          A = [x y;y z];
          a = eig(A);
          if (a(1) >= 0) && (a(2) >= 0)
              vecx(num) = x;
              vecy(num) = y;
              vecz(num) = z;
          else
              vecx(num) = NaN;
              vecy(num) = NaN;
              vecz(num) = NaN;
          end
      end
  end
end
%%picture
figure(1)
plot3(vecx,vecy,vecz,'.')
axis([0 1 -1 1 0 1])