surf plot behaves strange!
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Hi,
i generate a surface with surf. The problem is, that the coloring does not match the actual Data.
The Data is shown by the Z-Value in the surface (as usual). I uploaded the created Image. There i pointed out what i mean exactly:
How can the same color be attached to such different z-values?Is this a bug? Has anybody an idea how i can fix this?
Thanks for the attention
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답변 (2개)
Kevin Holst
2012년 6월 15일
Surf attaches a color to a face based on one point on that face, and each face will be created by 4 points, so that color may not make sense for 3 of those points. This is especially true when there is a lot of variation point to point.
What I typically do is set shading to interp either within the call to surf itself or after the call.
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Kevin Holst
2012년 6월 18일
Your top picture shows surf(data) which plots each data sample versus its row/column numbers. So your data matrix must be something close to size of 50x560. The reason that when you use meshgrid, you're getting a different looking plot is because it appears that there aren't 560 distinct values in the y-direction. It appears that some are repeated due to the resolution of your y-variable.
One color makes sense (programatically) for those two points you show because of how the surf function attaches a color to a surface face by default. It requires 4 points to make a face, and it chooses 1 of those 4 points to base the color of the face on.
Walter Roberson
2012년 6월 15일
The colors of a surf() plot or a pcolor() plot are not directly derived from the Z value of individual points. Instead they are interpolated from nearby points. See http://www.mathworks.com/help/techdoc/ref/surf.html under "Algorithms"
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Kevin Holst
2012년 6월 15일
What you described is what happens when using shading interp, which is not the default. The default is faceted in which "each mesh line segment and face has a constant color determined by the color value at the endpoint of the segment or the corner of the face that has the smallest index or indices.'
http://www.mathworks.com/help/techdoc/ref/shading.html
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