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Cirle with color changing gradually.

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How can I plot a circle like this in matlab, please give me an example. Thanks in advance.

Accepted Answer

arich82
arich82 on 17 Jul 2015
Edited: arich82 on 17 Jul 2015
[Edited to add colorbar and image.]
As far as I know, you can't do it directly, but pol2cart is your friend. Look at
and maybe
% construct grid of polar coords
th = (0:5:360)*pi/180;
r = 0:.05:1;
[TH, R] = meshgrid(th, r);
% convert polar to cartesian
[X, Y] = pol2cart(TH, R);
% dummy function plotted over X Y data
Z = X + 1i*Y;
f = abs((Z.^4 - 1).^(1/4));
% use overhead view of surf plot for figure
figure;
surf(X, Y, f);
view(2);
axis equal;
axis square;
colorbar('SouthOutside');
colormap('Jet');
Note that axis(2) gives an overhead view, so it looks like a flat circle, and axis equal ensures it looks like a circle and not a distorted ellipse.
Please accept this answer if it helps, or let me know what's wrong in the comments.
  6 Comments
Walter Roberson
Walter Roberson on 18 Mar 2017
Unfortunately, surf() is not compatible with the new-ish polaraxes (R2016a and later).
You could use the older polar() to create the basic background graphic, and then "hold on", and then plot on top of it.

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More Answers (1)

Walter Roberson
Walter Roberson on 18 Mar 2017
The File Exchange contribution https://www.mathworks.com/matlabcentral/fileexchange/17933-polar-to-from-rectangular-transform-of-images transforms rectangular images to and from polar to achieve the effect this Question is about.

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