Cirle with color changing gradually.

% 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.

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arich82 2015-7-20

在 MATLAB Online 中打开

The above works for precisely this case, assuming you have data on a regular grid of (r, th) coordinates. If not, you'll probably have to interpolate.

Do you have data sampled at, e.g., theta every 5deg th = (0:5:360)*pi/180 and along the radius at every 5cm r = (0:0.05:1)? If you do, that's what's plotted above (you could trivially change the grid spacing for theta on a 1deg spacing via th=(0:1:360)*pi/180, and likewise for r).

If your data is sampled at random (r, th) pairs (i.e. a scatter plot), then the best method for interpolation will depend on both the version of Matlab you're using, and the nature of your data. I'll use scatteredInterpolant with the natural method in Matlab 2014a as an example.

I assume you already have values for r, th, and f, so the following is just dummy data for my example:

% dummy data sampled randomly
rng('default');
n = (72+1)*(20+1)
th = rand(n, 1)*2*pi;
r = rand(n, 1);
[x, y] = pol2cart(th, r);
f = abs(((x + 1i*y).^4 - 1).^(1/4)); % just dummy data; let f be your real data
figure;
scatter3(x, y, f, 10, f, 'filled');
view(2)
axis equal;
axis square;
colorbar('SouthOutside');
colormap('Jet');
caxis([0, 1.189207115002721]); % colorbar limits from previous plot, for comparison
title('scatter plot of randomly sampled data')

We'll proceed as before generating a regular grid in r--|th| space, but use our vector of randomly sampled data to create an interpolating object. We'll interpolate on our regular grid, convert the grid to cartesian using pol2cart as before, and plot as before. (So the only extra step is creating the interpolant object, then interpolating.):

[TH, R] = meshgrid((0:5:360)*pi/180, 0:0.05:1);
f_interp = scatteredInterpolant(r, th, f, 'natural');
F = f_interp(R, TH);
[X, Y] = pol2cart(TH, R);
figure; 
surf(X, Y, F);%, 'EdgeColor', 'none'); 
view(2);
axis equal;
axis square;
colorbar('SouthOutside');
colormap('Jet');
caxis([0, 1.189207115002721]); % colorbar limits from previous plot, for comparison
title('reconstructed data');

Note that, in the scattered plot, there was a sparsely sampled region in the 3-o'clock position, and in the reconstructed plot, there's a bit of a yellow artifact in the same place, when compared to the original plot shown in the answer above.

Does this help?

Hoang Phuc Ho 2015-8-5

Thank you so much. It worked! :)

Walter Roberson 2017-3-18

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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Answer 2

Walter Roberson 2017-3-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/230238-cirle-with-color-changing-gradually#answer_259327

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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Aboozar Garavand 2017-3-19

Thank u, I solve the problem

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Cirle with color changing gradually.

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Cirle with color changing gradually.

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