How to find the number of point inside the graph?

Question

Ellina 2015-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/217703-how-to-find-the-number-of-point-inside-the-graph

评论： Andrei Bobrov 2015-5-21

Hello,

I have made a graph and inserted many random points.
I marked the point manually in orange color for points outside the graph and green color for points inside the graph
I wonder how can we calculate the number of points in green color automatically using only MATLAB code?

Thank you in advance

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Answer 1

Andrei Bobrov 2015-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/217703-how-to-find-the-number-of-point-inside-the-graph#answer_179764

编辑：Andrei Bobrov 2015-5-20

在 MATLAB Online 中打开

x = [0,7, 18, 37,47,54,57.5,59,61.5,69,87,95,99,103,110]'/110; % Let this
y = [0, 15,43,53,42,20,7,0, 37, 61,56, 40.5, 24, 6, 0]'/61;    % is arrays - your data
f = griddedInterpolant(x,y,'pchip'); % old MATLAB: pp = interp1(x,y,'pchip','pp'); 
                                     %             f = @(x)ppval(pp,x);
xx = rand(100,1);
yy = rand(100,1)*1.3; % points for check
t = f(xx) - yy > 0;
plot(0:.001:1,f(0:.001:1));grid on 
hold on
plot(xx(t),yy(t),'g*');
plot(xx(~t),yy(~t),'r*');