How to find 2D data points within a specific distance (in X and Y) to the inside direction along boundary line ?

In 2D data that has a boundary. How to find data points(x,y) which are laying within specific range from the boundary. For example :

https://www.mathworks.com/help/matlab/ref/boundary.html

x = gallery('uniformdata',30,1,1);

y = gallery('uniformdata',30,1,10);

plot(x,y,'.')

k = boundary(x,y);

hold on;

plot(x(k),y(k));

So, how can we get the data points(x,y) laying within distance of 0.5 in both directions x and y from the inside wall along the boundary. In other words, How can I get data points(x,y) that is (0.5 or less) away from the inside of the boundary wall in any direction (x,y).

Thanks

Answer 1

[KSSV]

Read about rangesearch

x = gallery('uniformdata',30,1,1);
y = gallery('uniformdata',30,1,10);
plot(x,y,'.')
k = boundary(x,y);
hold on;
plot(x(k),y(k));

%%get points at distance 0.5 from boundary 
idx = rangesearch([x y],[x(k) y(k)],0.5);
% plot the points
N = length(k) ;
for i = 1:N
    plot(x(idx{i}),y(idx{i}),'O','color',rand(1,3)) ;
end

[Faez Alkadi]

Thank you so much KSSV,

One more question please,

Do you know how can I delete this detected data points from the original matrix [x y] withOUT deleting boundary points with it. And make the code return NEW [X Y] matrix without detected points?

I added this to the for loop but didn't work:

 for i = 1:N

X=(x(idx){i});
Y=(y(idx){i});
  plot(x(idx{i}),y(idx{i}),'O','color',rand(1,3)) ;
end

Best

[John D'Errico]

The nice thing about Answers is all of us can learn from it. I never saw rangesearch until now. Learn something new everyday.

Answer 2

[Faez Alkadi]

Thank you so much KSSV,

One more question please,

Do you know how can I delete this detected data points from the original matrix [x y] withOUT deleting boundary points with it. And make the code return NEW [X Y] matrix without detected points?

I added this to the for loop but didn't work:

 for i = 1:N
X=(x(idx){i});
Y=(y(idx){i});
  plot(x(idx{i}),y(idx{i}),'O','color',rand(1,3)) ;
end

Best