How to find the number of point inside the graph?

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

Answer 1

[Andrei Bobrov]

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*');

[Ellina]

Thank you so much.

The logical code,t helps me a lot.

I already plotted the graph but I don't know how to count automatically the number of green point.

Still trying my best to code it.

[Andrei Bobrov]

number of green point:

NG = sum(t);

or

NG = nnz(t);