Get boundary of 2d mesh

i have a 3d mesh, i delete z axes and so i'll have 2d mesh. my question is how can i get boundary of the 2d mesh?

[Rik]

What form of data is your mesh in? You might be able to use something like inpoly.

Answer 1

[KSSV]

Read about boundary function.

%%Structured data 
[X,Y,Z] = peaks(100) ;
idx = boundary(X(:),Y(:)) ;
figure
plot(X,Y,'.r') ;
hold on
plot(X(idx),Y(idx),'.-b')
%%Unstructured data 
x = rand(100,1) ; y = rand(100,1) ;
idx = boundary(x,y) ;

figure
plot(x,y,'.r')
hold on
plot(x(idx),y(idx),'.-b')

Answer 2

[Aref Hemati]

thanks kssv, I tried to use boundry function but as you see in below image, it's not cover all points in boundry, especially around red region sign (I zoom in on area). Even though i used 1 as shrink factor.

k = boundary(xpoints,ypoints,1);

[Image Analyst]

Try different shrink factors. Attach your 2-D data if you need more help.