How can i rotate an ellipse?

Question

anderson95 2017-5-27

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https://ww2.mathworks.cn/matlabcentral/answers/342148-how-can-i-rotate-an-ellipse

回答： MathReallyWorks 2017-5-27

Im wondering how i can rotate an ellipse to a bearing/azimuth of 30deg about the xcenter and ycenter. Below is an example of how i have plotted the ellipse.

Thanks

xCenter = 50;

yCenter = 50;

xRad = 25;

yRad = 100;

theta = 0 : 0.01 : 2*pi;

x = xRad * cos(theta) + xCenter;

y = yRad * sin(theta) + yCenter;

plot(x, y, 'r');

axis([-50 150 -100 200]);

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Answer 1

MathReallyWorks 2017-5-27

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https://ww2.mathworks.cn/matlabcentral/answers/342148-how-can-i-rotate-an-ellipse#answer_268638

在 MATLAB Online 中打开

Hello,

Use this:

 clc;
xc=50; %xCenter
yc=50; %yCenter
a=25; %xRad
b=100; %yRad
m = 1000;
x = zeros(m,1);
y = zeros(m,1);
theta = linspace(0,2*pi,m);
for k = 1:m
        x(k) = a * cos(theta(k));
        y(k) = b * sin(theta(k));
end
alpha = input('Enter the rotation angle');
R  = [cos(alpha) -sin(alpha); ...
      sin(alpha)  cos(alpha)];
rCoords = R*[x' ; y'];   
xr = rCoords(1,:)';      
yr = rCoords(2,:)';      
plot(x+xc,y+yc,'r');
grid on;
hold on;
axis equal;
plot(xr+xc,yr+yc,'b');