How to create a perimeter from x,y coordinates

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Alex castilla 2018-3-20

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评论： Alex castilla 2018-3-22

Hello everybody,

I have a small question:

I have two matrices: A(2099x2) and B(9x4).

Matrix A = trajectory (x,y)

Matrix B = X,Y position of 9 (black square dots), the width=0.20 and the height= 0.20.

I would like to know how to create a perimeter around of the black square dots (green square) and calculate if the trajectory (blue line) enter in this perimeter. Thanks in advance

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Guillaume 2018-3-20

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The easiest way, assuming R2017b or later, is to use the intersect method of the polyshape object, which you can construct either by providing the 4 corners of your perimeter or with nsidedpoly:

perimeterside = 0.2;  
for blackdotidx = 1:size(B, 1)  %iterate over the black dots
   perimeter = nsidedpoly(4, 'Center', A(blackdotidx, :), 'SideLength', perimeterside);
   if ~isempty(intersect(perimeter, A))  
        %1st output of intersect is segments inside the perimeter, so if not empty there is intersection
        fprintf('trajectory intersect perimeter %d\n', blackdotidx);
   end
end