How to plot ellipse using contour function?
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i would like to plot ellipse using contour function, since it is easier to label curves or lines than plot function , but it does not show the expected lines, the lines should be narrowed towards left and not towards right
%If_dmax is an array (1*201)
%[X,Y] = meshgrid(linspace(-1000,1000,201),linspace(-1000,1000,201));
for k1 = 1:(length(If_dmax))
[C,fContour] = contour(X,Y,sqrt((L_d.*X+L_df*If_dmax(k1)).^2+(L_q.*Y).^2),'ShowText','on', 'LineWidth', 0.5,'EdgeColor',[0 0 1]);
%fContour.LevelStep=0.05;
end
8 件のコメント
Torsten
2023 年 3 月 13 日
t = 0:0.01:2*pi;
a = [1;2];
b = [2;4];
x = a*cos(t);
y = b*sin(t);
plot(x.',y.')
回答 (1 件)
John D'Errico
2023 年 3 月 13 日
編集済み: John D'Errico
2023 年 3 月 13 日
I'm a little confused. You DID draw ellipses. It seems the goal was not to draw the ellipses you drew though. Essentially, as you did it, you drew ellipses of the form:
(x/a)^2 + (y/b)^2 = R
where R varies, but a was fixed. That is how contour would work, and you were triyng to use contour to solve your prolem. I imagine you saw someone using contour to draw ellipses online somewhere. It may even have been me who showed that trick.
But from your comment, you seem to be asking how to draw ellipses where a varies in the espression
(x/a)^2 + (y/b)^2 = 1
Essentially, that will cause each ellipse to be wider or narrower in the x-direction. Possibly then, a better method is to just use polar coordinates. For example, I'll choose to vary a in that expression, where b is fixed at 1.
b = 1;
theta = linspace(0,2*pi)';
a = 0.25:0.25:2;
x = zeros(size(theta))*a;
% note that I could have done this without using a loop at all, but that
% may have been too much to understand how it works.
for i = 1:numel(a)
x(:,i) = a(i)*cos(theta);
y(:,i) = b*sin(theta);
end
plot(x,y)
legend(string(a))
4 件のコメント
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