How to draw a rotated ellipse without any toolbox?
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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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Accepted Answer
Babak
on 28 Aug 2012
Edited: Babak
on 28 Aug 2012
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
3 Comments
Image Analyst
on 2 Sep 2012
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
on 9 Dec 2019
Edited: Gabriel Hernandez
on 9 Dec 2019
This code did not work for me. The answer posted below is much more accurate.
More Answers (1)
Oleksii Sidorov
on 26 Feb 2018
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;
2 Comments
Gabriel Hernandez
on 9 Dec 2019
Your code worked perfectly for me, much better than the one from the accepted answer. Thank you!
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