How to draw a rotated ellipse without any toolbox?

Question

ManKit Tse 2012-8-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/46908-how-to-draw-a-rotated-ellipse-without-any-toolbox

评论： Vivek Bhartiya 2020-3-30

I need to draw rotated ellipse on a Gaussian distribution plot by surf. I am using a student version MATLAB. Can i still draw a ellipse center at estimated value without any toolbox that required money to buy. I search on internet somebody write ellipse function and allow to download. Are they work well on surf plot.

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Answer 1

Babak 2012-8-28

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https://ww2.mathworks.cn/matlabcentral/answers/46908-how-to-draw-a-rotated-ellipse-without-any-toolbox#answer_57319

编辑：Babak 2012-8-28

在 MATLAB Online 中打开

 t = linspace(0,2*pi,1000);
 theta0 = pi/6;
 a=2;
 b=1;
 x = a*sin(t+theta0);
 y = b*cos(t);
 plot(x,y)
 axis equal

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Image Analyst 2012-9-2

Well yeah, because if a or b is really close to zero, the width is really close to zero and the ellipse is essentially almost a line. And a line has to lie along the raster lines on your monitor. The line can be on line 1 or on line 2. You can't have pixels going across the screen at line 1, line 1.01, line 1.02, etc. up to line 1.88 or whatever. It's got to be just on line 1 or on line 2, not on fractional lines. For further reading: http://en.wikipedia.org/wiki/Jaggies

Gabriel Hernandez 2019-12-9

编辑：Gabriel Hernandez 2019-12-9

This code did not work for me. The answer posted below is much more accurate.

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Answer 2

Oleksii Sidorov 2018-2-26

7
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/46908-how-to-draw-a-rotated-ellipse-without-any-toolbox#answer_307189

在 MATLAB Online 中打开

My version with general parametric equation of rotated ellipse, where 'theta' is angle of CCW rotation from X axis (center at (x0, y0))

 t = linspace(0,2*pi,100);
 theta = deg2rad(105);
 a=2;
 b=1;
 x0 = 0.15;
 y0 = 0.30;
 x = x0 + a*cos(t)*cos(theta) - b*sin(t)*sin(theta);
 y = y0 + b*sin(t)*cos(theta) + a*cos(t)*sin(theta);
 figure;
 plot(x,y);
 axis equal;