function handles
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hei guys,i have a problem with function usage and i kinda get confused with it .my function works when i change the position of the polygon (created with impoly), and it will automatically call the second function that make a new patch that fill the polygon new position. the problem is when i change the position of the polygon, the function keeps on making new patches. is there a way to fill colors while we change the polygon's position?
here is the script that i've wrote
function polygon
axis([0 100 0 100])
h = impoly(gca,[10 10 ; 20 10; 20 20 ; 10 20]);
api = iptgetapi(h);
current_body_coordinates = api.getPosition();
patches(current_body_coordinates)
api.addNewPositionCallback(@patches);
function patches(p)
patches=patch(p(:,1),p(:,2),'r');
thanks in advance :D
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Answers (1)
Pratyush Swain
on 21 Mar 2025
Hi Mallory,
The problem arises because each time the polygon's position changes, a new patch is created without removing the previous one.
We can update the position of the patch instead of creating a new patch each time:
function polygon
axis([0 100 0 100])
% Create the polygon
h = impoly(gca,[10 10 ; 20 10; 20 20 ; 10 20]);
api = iptgetapi(h);
current_body_coordinates = api.getPosition();
% Create a patch using the initial position
poly_patch = patch(current_body_coordinates(:,1), current_body_coordinates(:,2), 'r');
% Callback to update the patch
api.addNewPositionCallback(@update_patch);
% Function to update patch
function update_patch(p)
set(poly_patch, 'XData', p(:,1), 'YData', p(:,2));
end
end
For more information on 'patch' function, you can refer to - https://www.mathworks.com/help/matlab/ref/patch.html
Hope this helps.
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