# Order Points for plotting

10 views (last 30 days)
Ahmed Abdulla on 24 May 2022
Commented: Ahmed Abdulla on 24 May 2022
I have the coordinates of the above two shapes imported from a CAD software, however when I plot the shape the points are not in order. Is there a method to order the coordinates so that points on the perimeter of the shape that are side by side are next to each other in the matrix.
If there is any mathematical method that would help me, I am willing to understand it and code it myself. Thank you
Walter Roberson on 24 May 2022
use a different shrink factor?
Ahmed Abdulla on 24 May 2022
@Walter Roberson Here I am using a shrink factor of 1 which is the highest I can go :(

KSSV on 24 May 2022
x = A(:,1) ; y = A(:,2) ;
n = length(x) ;
iwant = zeros(n,2) ;
i = 1 ;
iwant(i,:) = [x(i) y(i)] ;
x(i) = [] ; y(i) = [] ;
while ~isempty(x)
i = i+1;
idx = knnsearch([x y],iwant(i-1,:));
iwant(i,:) = [x(idx) y(idx)] ;
x(idx) = [] ; y(idx)= [];
end
iwant(end+1,:) = iwant(1,:) ;
plot(iwant(:,1),iwant(:,2))
##### 3 CommentsShow 1 older commentHide 1 older comment
KSSV on 24 May 2022
Edited: KSSV on 24 May 2022
Lets randomize the points and run the code.
x = A(:,1) ; y = A(:,2) ;
n = length(x) ;
idx = randperm(n,n) ;
x = x(idx) ; y = y(idx) ;
iwant = zeros(n,2) ;
i = 1 ;
iwant(i,:) = [x(i) y(i)] ;
x(i) = [] ; y(i) = [] ;
while ~isempty(x)
i = i+1;
idx = knnsearch([x y],iwant(i-1,:));
iwant(i,:) = [x(idx) y(idx)] ;
x(idx) = [] ; y(idx)= [];
end
iwant(end+1,:) = iwant(1,:) ;
plot(iwant(:,1),iwant(:,2))
Ahmed Abdulla on 24 May 2022
Thank you @KSSV for your efforts I really appreciate it. Unfortunately this doesnt work every time and I am trying to make a generalised function that will work for any shape and at all times

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