surf plot behaves strange!

8 views (last 30 days)
Miro
Miro on 15 Jun 2012
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

Answers (2)

Kevin Holst
Kevin Holst on 15 Jun 2012
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 Comments
Kevin Holst
Kevin Holst on 18 Jun 2012
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.

Sign in to comment.


Walter Roberson
Walter Roberson on 15 Jun 2012
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 Comments
Miro
Miro on 18 Jun 2012
exactly. And this works fine if i plot the data without a specified meshgrid. But when i use the dimensioned grid, the problem occurs. The y-Axis is a time vector, and the time is not continuous, could that possibly be the reason?

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by