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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回答 (2 件)
Kevin Holst
2012 年 6 月 15 日
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.
2 件のコメント
Kevin Holst
2012 年 6 月 18 日
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
2012 年 6 月 15 日
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"
2 件のコメント
Kevin Holst
2012 年 6 月 15 日
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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