How to plot solid concentric circles in a meshgrid?

Question

Viron Gil Estrada 2018-3-14

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/388287-how-to-plot-solid-concentric-circles-in-a-meshgrid

回答： Star Strider 2018-3-14

I am trying to plot solid concentric circles in a meshgrid but the code I used only plots the borders of the circles.

 theta = linspace(0, 2*pi, 100);
[X, Y] = meshgrid(1:1:4, theta);
a = 0;
b = 0;
plot(a+cos(Y).*X, b+sin(Y).*X);
axis equal

What I intend to do is to generate solid concentric circles and that the points inside the circles are valued as either 1 (white) or 0 (black). Below is a picture for visualization. Can anyone help me?

Thanks,

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Answer 1

Star Strider 2018-3-14

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/388287-how-to-plot-solid-concentric-circles-in-a-meshgrid#answer_310032

在 MATLAB Online 中打开

Try this:

theta = linspace(0, 2*pi, 100);
[X, Y] = meshgrid(1:1:4, theta);
a = 0;
b = 0;
figure(2)
plot(a+cos(Y).*X, b+sin(Y).*X);
axis([-1  1    -1  1]*6)
hold on
patch([xlim fliplr(xlim)], [min(ylim)*[1 1] max(ylim)*[1 1]], 'k')
for k1 = 4 : -1 : 1
    color = [1 1 1]*(mod(k1,2)==0);
    patch(a+cos(Y(:,k1)).*X(:,k1), b+sin(Y(:,k1)).*X(:,k1), color);
end
hold off
axis equal
axis tight

It creates patch objects going from the largest radius to the smallest, changing the colours with each iteration of the for loop. It colours the background black first. If you want a larger background, area, increase the multiplier (here 6) in the axis call.

Experiment to get the result you want.