# Line pathway using intersection points

1 view (last 30 days)
Tchilabalo on 29 Aug 2019
Commented: darova on 8 Sep 2019
clear all
Window=10
square=[0 0; 0 Window; Window 0; Window Window];% Box coordinates
N=5;
% Coordinates of segments endpoints
X1=rand(N,1)*(10+0.1)+0.1;
X2=rand(N,1)*(10+0.1)+0.1;
Y1=rand(N,1)*(10+0.1)+0.1;
Y2=rand(N,1)*(10+0.1)+0.1;
A = [X1(:), X2(:)]; B =[Y1(:), Y2(:)];
% Find the intersection between segments
% Here i use the intersection function by Douglas M. Schwarz
ABx=[X1(:), X2(:)];
reshape(ABx,1,[]);
transpose(ABx);
ABx.';
ABx(:);
ABx=reshape(ABx.',1,[]);
ABy=[Y1(:), Y2(:)];
reshape(ABy,1,[]);
transpose(ABy);
ABy.';
ABy(:);
ABy=reshape(ABy.',1,[]);
pos = 3:3:((((length(ABy))/2)-1)*3);
[r,c] = size(ABy);
Xnew(1,idx) = ABx;
Ynew(1,idx) = ABy;
Inter=intersections(Xnew,Ynew);% This gives the intersection points
figure, plot(A.',B.','LineWidth', 0.75)
grid on
axis square
axis([0 Window 0 Window]) I have segments as shown above. For each segment, i have the coordinates of endpoints. Now, I want to determine the pathways that connect both sides of the box, and remove the unconnected segments. So far, i have been able to find the intersections betweeen segments, and will appreciate any help finding the pathways.

darova on 30 Aug 2019
How would you know the order of connections? Tchilabalo on 30 Aug 2019
By sorting the intersections in increasing order of x and y.
darova on 30 Aug 2019
SO what is the question? You have all points. Why don't just use plot()?

darova on 30 Aug 2019
Simple example
n = 5;
x1 = rand(n,2);
y1 = rand(n,2);
x2 = rand(n,2);
y2 = rand(n,2);
k = 0;
% loop through all segment to find all intersections
for i = 1:n
for j = 1:n
[xc,yc] = polyxpoly(x1(i,:),y1(i,:),x2(j,:),y2(j,:));
if ~isempty(xc)
k = k+1;
x(k) = xc;
y(k) = yc;
end
end
end
[~, ix] = sort(x);
plot(x(ix),y(ix),'o-k','linewidth',2)
hold on
plot(x1',y1','r',x2',y2','b')
hold off

Tchilabalo on 30 Aug 2019
darova on 8 Sep 2019
Accept the answer if it helped