Plotting a complex inequality

Question

Su_pat 2020-4-13

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517492-plotting-a-complex-inequality

回答： Ameer Hamza 2020-4-13

采纳的回答： Ameer Hamza

Is there any way in Matlab that I can plot this inequality?

q(2p1+p2+p4 -1) <= 2sqrt [ (qp2 + (1-q)/4))*(qp4 + (1-q)/4) ] where q,p1,p2 and p4 are between 0 and 1.

So I have 2 complications here,

How to plot an inequality?
How to plot 4 variables? Can I use color schemes or contour plotting?

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Answer 1

Ameer Hamza 2020-4-13

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517492-plotting-a-complex-inequality#answer_425700

在 MATLAB Online 中打开

For your first question. You can plot an inequality with two variables like this

q = 1;
p4 = 2;
[p1, p2] = meshgrid(linspace(0,1,100));
s = q*(2*p1+p2+p4-1) <= 2*sqrt((q*p2 + (1-q)/4)*(q*p4 + (1-q)/4));
contourf(p1,p2,s+0, 'LineColor', 'flat');
xlabel('p1');
ylabel('p2');

For the second question, I am not sure how you can visualize it. With the help of slice(), it is somewhat possible to visualize 3 variables, but four variables cannot be visualized in a single graphic. Plotting several 2D plots by fixing the values of the other two variables is one of the ways.