I have some point and one line.

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Mili Kian 2020-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/519141-i-have-some-point-and-one-line

评论： Ameer Hamza 2020-4-21

采纳的回答： Ameer Hamza

在 MATLAB Online 中打开

I have some point and one line.

my points are in (x,y) written in under

and my line is

 r=[0 10 15 20 30];
 t=[10 10 15 10 10];
f= line(r,t)

how can i find wich points are under the line??

please help me its emergency

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David Welling 2020-4-19

Since there is only a small number of cases, you could do it by hand, especially since the line is so simple.

plot the line and the points and you will see it easily.

for a more general case using arbitrary points and lines, I suggest interpolating to find the y value of the line for a given x of the point, and then comparing y_line and y_point

Mili Kian 2020-4-20

these points were for example. in fact i have more than a hundread points.

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Answer 1

Ameer Hamza 2020-4-20

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https://ww2.mathworks.cn/matlabcentral/answers/519141-i-have-some-point-and-one-line#answer_427108

在 MATLAB Online 中打开

try this. X is the n*2 matrix given in your question

r=[0 10 15 20 30];
t=[10 10 15 10 10];
x = interp1(r,t, X(:,1));
mask = X(:,2) >= x;
plot(r, t, 'r', X(mask,1), X(mask,2), 'r*',  X(~mask,1), X(~mask,2), 'b*')