MATLAB: Determine if a point lies between two lines

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Assume there are two lines and each line is defined by two points.(e.g. (x1a,y1a) and (x2a,y2a) for line 1, (x1b,y1b) and (x2b,y2b) for line 2.). Consider also a square centered at the origin therefore these points are inside the square. How can we test whether a point inside the square (xu,yu) lies between these lines? Lines can be either parallel or intersecting (in such case, lines intersect outside the square).
     %line 1
    x1a=-2.5;
    y1a=-1.8;
    x2a=0.8;
    y2a=-2.5;
    %line2
    x1b=-2.5;
    y1b=- 1.4; 
    x2b=2.5;
    y2b=1.4;
    %square
    xs=[-2.5 -2.5 2.5 2.5 -2.5] ;
    ys=[-2.5  2.5 2.5 -2.5 -2.5];
    figure;
    plot([x1a x2a],[y1a y2a])
    hold on
    plot([x1b x2b],[y1b y2b])
    hold on
    plot(xs,ys,'-k','Linewidth',2)
    axis([-3 3 -3 3])
Assume the lines and square created above. How can we exactly test if (2,-2) is between lines inside the square but (-1,1) is not?

Best Answer

You can use inpolygon.
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