An error while using polyxpoly for finding (xi,yi) of an intersecting line and circle

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I need to connect point 2 and point 1 and find all the intersecting points(between red line and blue line/circle), So, I used polyxpoly. My problem is why polyxpoly function generates an extra intersecting point which is not on the line or the circle (I show it in the below image)?
My data
clear variables
% points
% line coordinates
% Circle coordinates
xcenter = 2;
ycenter = 2;
radius = 1;
circr = @(radius,rad_ang) [radius*cos(rad_ang)+xcenter; radius*sin(rad_ang)+ycenter];
N = 2000;
rad_ang = linspace(0, 2*pi, N);
xy_r = circr(radius,rad_ang);
x_circle= radius * cos(rad_ang) + xcenter;
y_circle= radius * sin(rad_ang) + ycenter;
% all points
% I want to calculate the intersection coordinates between a line contacting curret point/next point and
% circle/line
All([next_point;current_point],2),[x_line;circle(:,1)], [y_line;circle(:,2)])

Accepted Answer

Pratyush Roy
Pratyush Roy on 1 Oct 2020
The x co-ordinates as well as the y co-ordinates of the line and the circle should not be combined as this generates a complicated polygon and a new solution is found other than the expected ones.
As a workaround one can use the polyxpoly function twice to generate two sets of solutions which together will provide the expected solution.
[xi,yi]= polyxpoly(All([next_point;current_point],1),...
Here [xi,yi] will give us the points of intersection between the line and the circle and [xj,yj] will give us the point of intersection between the two lines.
Hope this helps!
  1 Comment
Zarak kh
Zarak kh on 9 Oct 2020
Dear Pratyush,
Thanks a lot for your help, it is indeed helpfull. According to your explanation is it okay to also add "NaN" in polyxpoly function like below?
All([next_point;current_point],2),[x_line;NaN;circle(:,1)], [y_line;NaN;circle(:,2)])

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