Problems plotting and adding legend to certain point in a plot

Question

Ryan Davidson 2020-11-9

0
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https://ww2.mathworks.cn/matlabcentral/answers/642070-problems-plotting-and-adding-legend-to-certain-point-in-a-plot

回答： Setsuna Yuuki. 2020-11-10

Hi,

I have a simple code that plots 7 eigenvalues as follows:

A = load('XV15A_200kts_A9.txt');

Result = eig(A)

plot(Result,'+')

What I would like to do is for pairs of points (ie -2 + 0.5i and -2 - 0.5i) to have a different colour to other points and I would ideally like to label these points in the legend (so in this example i would like the two points to be marked red and in the legend say 'Dutch Roll Mode')

Any help would be appreciated

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Answer 1

Setsuna Yuuki. 2020-11-10

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/642070-problems-plotting-and-adding-legend-to-certain-point-in-a-plot#answer_539745

在 MATLAB Online 中打开

to place the dots with different colors:

compleja = 0;
A = rand(100);
result = eig(A)
j = 1;
for i = 1:length(result)-1
    if(result(i) == conj(result(i+1)))
       compleja(j) = result(i);
       j = j+1;
    end
    
end
result = result(2:length(result));
resultReal = real(result); resultComplex = imag(result);
scatter(resultReal,resultComplex,'g +','linewidth',2); hold on;
resultReal = real(compleja); resultComplex = imag(compleja);
scatter(resultReal,resultComplex,'r +','linewidth',2)
compleja = conj(compleja);
resultReal = real(compleja); resultComplex = imag(compleja);
scatter(resultReal,resultComplex,'b +','linewidth',2)
xlabel('Real'); ylabel('Imaginario')
legend('Only Real','Red category','Blue category')