coloring the area between three curves

Hi. I want to color the intersection region of three curves.

T1 = 180:0.1:270;

x1 = 3*cosd(T1); y1 = 3*sind(T1); % circle

T2 = 3.3620:0.001:3.9045;

c1 = 4.3123; c2 = -50.2708; c3 = 193.7277; c4 = -243.8411;

r_6 = c1*T2.^3 + c2*T2.^2 + c3*T2 + c4;

x2 = 1.1998 + r_6.*cos(T2); y2 = -0.8840 + r_6.*sin(T2); % region 4

x0 = 1.8977; y0 = 2.3235; vr = 4.0678;

beta = atan(y0/x0);

x3 = -2.0591:0.001:-1.8541; y3 = y0 + (x0-x3)*cot(beta) - (9.81*(x0-x3).^2)./(2*(vr*sin(beta))^2); % parabola

pgon1 = polyshape(x1,y1); % circle

pgon2 = polyshape(x2,y2); % region 4

pgon3 = polyshape(x3,y3); % parabola

pgon4 = intersect(pgon1,pgon2);

figure (4)

plot(x1,y1,x2,y2,x3,y3)

hold on

plot (intersect(pgon3,pgon4),'EdgeColor','none')

Actually, the fucntion :plot (intersect(pgon3,pgon4),'EdgeColor','none'); gives the error

Please suggest a way

Answer 1

[Pranjal Kaura]

Hey Mukesh,

The common area between the polygons 'pgon3' and pgon4' isn't being plotted because the 'intersect' function doesn't find any common points between the 2 regions and thus returns an object having an empty matrix for 'Vertices' field, when you run

>> intersect(pgon3,pgon4)

To visualise your plots better, you can try plotting the polygon regions ('pgon1', 'pgon2' etc one after the other) and then decide which polygons to send to the 'intersect' function to compute the common points. You can refer the following code snippet:

>> figure
>> hold on
>> plot(pgon3)
>> plot(pgon1)
>> plot(pgon2)

You can check the 'Vertices' field of the 'polyshape' object that the function 'intersect' returns to confirm whether there are any common points.

Hope this helps!