use surf() to plot a circle from a rectangle matrix

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Marvin Lochmann
Marvin Lochmann 2019-1-4
回答： Image Analyst 2019-1-4
Hey everybody,
I have a greyscale picture and i want to surface plot just a circle from it.
I tried to cut out the circle and plot it with surf(). It didnt work.
After that, i tried to assign NaN to the values i dont want to plot. But they are plotted as zeros. I didnt find a way to ignore those values.
i attached the picture file i am using.
What am i doing wrong?
Im a real Matlab beginner by the way.
Scan_rec0254.bmp

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回答（2 个）

Cris LaPierre
Cris LaPierre 2019-1-4
Sure. See this StackExchange post about exactly this. I'm copying the code below
[x, y] = ndgrid(linspace(-1,1,500));
z = cos(2*pi*(x+y)*2);
z(x.^2+y.^2>1) = NaN; %// remove values outside unit circle
surf(x,y,z,'edgecolor','none')
colorbar
view(2)
axis equal
view(2) creates a top down view.
bdYRD.png
view(3) creates a 3d view
surfCircle.png
Image Analyst
Image Analyst 2019-1-4

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