How to "color" the closed area bounded by three curves

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mukesh bisht
mukesh bisht 2021-11-12
编辑： Simran 2025-4-29
Ran in:
Hi, I want to color the area between the intersection of three curves. Please suggest a way.
Code Updated by @Sam Chak: (based on info in Comment)
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, 'linewidth', 2)
hold on
plot(intersect(pgon3, pgon4), 'EdgeColor', 'none')
grid on
axis equal
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Star Strider
Star Strider 2021-11-12
Ran in:
... still more problems ...
T2 = 3.3620:0.001:3.9045;
T1 = 180:0.1:270;
x1 = 3*cosd(T1); y1 = 3*sind(T1);
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 = 1.998 + r_6.*cos(T2); y2 = -0.8840 + r_6.*sin(T2);
x0 = 1.8977; y0 = 2.3235; vr = 4.0678;
beta = atan(y0/x0);
x3 = s2(1,1):0.001:x_t; y3 = y0 + (x0-x3)*cot(beta) - (9.81*(x0-x3).^2)./(2*(vr*sin(beta))^2);
Unrecognized function or variable 's2'.
pgon1 = polyshape(x1,y1);
pgon2 = polyshape(x2,y2);
pgon3 = polyshape(x3,y3);
figure (1)
plot(x1,y1,x2,y2,x3,y3)
hold on
plot (intersect(intersect(pgon3,pgon4)), pgon3,'EdgeColor','none')
I would really like to be able to run this in order to see what the problems are.
.
mukesh bisht
mukesh bisht 2021-11-13
sorry for my incorrect code. Here, is the final corrected version
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')
I want to color the area of intersection of these threee curves

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回答（1 个）

Simran
Simran 2025-4-28
编辑：Simran 2025-4-29
Hey @mukesh bisht,
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 refer to the below documentation links:
'intersect' - https://www.mathworks.com/help/matlab/ref/double.intersect.html
'polyshape' - https://www.mathworks.com/help/matlab/ref/polyshape.html?s_tid=doc_ta

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