Contourf: fill inside instead of outside

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Marco Sammito
Marco Sammito 2019-4-7
评论： DGM 2024-7-26
Hi, how can I fill the area within the circle? At the moment Matlab fills the area outside. I would like the outside to be white and the inside to be filled. Thanks.
relamdt=-4:0.1:4;
imlamdt=-4:0.1:4;
[x,y]=meshgrid(relamdt,imlamdt);
axis square;
lamdt=x+i*y;
sig = (1 + lamdt);
v = [1,1];
contourf(x,y,abs(sig),v)
Screenshot_2019-04-08_09-54-58.png

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采纳的回答

Walter Roberson
Walter Roberson 2019-4-8
编辑：Walter Roberson 2019-4-8
contourf(x, y, -abs(sig), -v)
Alternately, possibly
[~,h] = contourf(x, y, abs(sig), v);
drawnow(); %seems to be needed to get NodeChildren created
bg = h.NodeChildren(2).ColorData;
h.NodeChildren(2).ColorData = uint8([255; 255; 255; 255]);
ax = ancestor(h,'axes');
ax.Color = bg;

更多回答（2 个）

David Wilson
David Wilson 2019-4-8
A quick hack (following the essence of your code) is
cmap = colormap; cmap(end,:) = [1,1,1]; colormap(cmap);
contourf(x,y,abs(sig),[0,1]);
axis square
  1 个评论
Marco Sammito
Marco Sammito 2019-4-8
It does not seem to affect anything. The area within the circle is still white: the outside is still green. I would like to invert these two. Inside=green, outside=white.

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Roberto Tumolo
Roberto Tumolo 2024-7-26
What if one wants to extract the values shown inside and outside (suppose you don't know them because they come from a contour?
  1 个评论
DGM
DGM 2024-7-26
The way the question is posed makes it unclear what information we might have. From a contour()/contourf() object, we can know a set of discrete z-values associated with the given level curves, but unless we have access to the original zdata, we don't know the actual values between the level curves. If we don't have access to the object itself (e.g. if all we have is a saved figure as a raster image (a screenshot)), then things get more restricted.

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