Determining point is within polygon or outside.

so far I have coded a profile and a user input to plot the points if inside or outside. any improvement to the code is appreciable

[Ramesh Bala]

%polygonal coordinates
close all

clear

clc

xv = [0 0 0 20  20 0 10 20 20 20 20 30 30 50 50 20 30 40 50]

yv = [0 0 50 10  0 0  0 0  0 10 50 50 10  10 0   0 0   0 0 ]

% plotting the points as polygonas
figure (1)

plot(xv, yv,'-')

hold on

%square axis
grid on
axis([-10 60 -10 60])

%specifying the N coordinate

% xq = [22 45];
% yq = [25 35];

[X] = ginput(2);
[X] = round(X);

xq = X(1:2);

yq = X(3:4);

%polygon and point plotting
[in,on] = inpolygon(xq,yq,xv,yv);

%Determine the number of points lying inside or on the edge of the polygon area.

   numel(xq(in))

%Determine the number of points lying on the edge of the polygon area.

numel(xq(on))

%Determine the number of points lying outside the polygon area (not inside or on the edge).

numel(xq(~in))

%Plot the polygon and the query points. Display the points inside the polygon with a red plus. Display the points outside the polygon with a blue circle.

figure (1)

plot(xv,yv) % polygon
axis([-10 60 -10 60])

hold on

plot(xq(in),yq(in),'r+') % points inside

plot(xq(~in),yq(~in),'bo') % points outside

hold off

[Adam Danz]

Also see

https://www.mathworks.com/matlabcentral/answers/411893-how-to-say-the-third-selected-point-lies-within-the-created-geometry-or-not

In this updated code, what is 'in' and 'on'? Or is that where you're stuck? If that's where you're stuck, how does this question differ from the previous one?

[Ramesh Bala]

Guten tag The question is similar I guess Except I don't know how to put this as an updated code in the previous one , that's why made a new one.

In means inside polygon ,on denotes on the polygon line. But I tried with numel(xq(in)) == numel(xq(-on)

[Ramesh Bala]

numel(xq(in)) > numel(xq(-in)) But it still says points inside the profile

[Adam Danz]

When I run the code you shared, 'in' is not defined anywhere. 'in' has no values. So the code breaks when it tries to execute 'in'.

[Ramesh Bala]

In on comes as ans and it gets window. I guess it should not be defined? I may be wrong too, kindly show me with an assigned value to it and how it works

[Adam Danz]

'in' and 'on' have no values. If you run the code you provided, it will break when it tries to execute 'in'. I don't know what 'in' and 'on' represent or what their values 'should' be. I'm guessing they are indices and their values are probably [0 1] or [1 0].

If you have a more clearer or specific question maybe I can help. But the biggest problem in your current code is that 'in' and 'on' have no values.

[Ramesh Bala]

Thanks für the reply. I actually tried using inpolygon for the code ,it didn't worked well as I'm selecting only 2 coords as user input .I think it works with random points. So here im trying to print a statement saying ginputs are within profile or outside profile using inpolygon Function. Actually the present code shows the points in and out in colours. I need to attach a print statement to it .

[Adam Danz]

Kaleesh,m see your other thread where I answered this question. inpolygon() does work well with your code.