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

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Faez Alkadi
Faez Alkadi 2017-7-31
回答： Faez Alkadi 2017-8-16
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

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采纳的回答

KSSV
KSSV 2017-8-3
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
  2 个评论
Faez Alkadi
Faez Alkadi 2017-8-3
编辑：Faez Alkadi 2017-8-3
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
John D'Errico 2017-8-3
The nice thing about Answers is all of us can learn from it. I never saw rangesearch until now. Learn something new everyday.

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更多回答（1 个）

Faez Alkadi
Faez Alkadi 2017-8-16
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

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