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How to smooth a contour plot?

Asked by Josh

Josh (view profile)

on 27 Feb 2014
Latest activity Answered by John D'Errico

John D'Errico (view profile)

on 27 Feb 2014

I have:

  • vector X: legnth(X)=90 --> X=[0:0.0125:1.1125]
  • vector Y: length(Y)=80 --> Y=[22.2: ...(not periodic)... :4]
  • matrix Z: size(Z)=90,80 --> measured values from each (X,Y) simulation

I am using contour(X,Y,Z), but am getting jagged, non-smooth contour lines, like this:

How do I smooth the contour lines? I've fiddled with trying to use interp2, but am falling down on the use of grid inputs I think.

Any help is much appreciated.



Josh (view profile)


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1 Answer

Answer by John D'Errico

John D'Errico (view profile)

on 27 Feb 2014
Accepted answer

You DON'T want to smooth the contour lines. That just never works out. Better (but rarely perfect) is to smooth the surface before the contours are built. I say not perfect because any time you do smoothing, you lose information too. Hey, life is tough.

The simple way to smooth the surface is to just use conv2, with a Gaussian blur as a kernel. Choose the width of the gaussian to adjust the amount of smoothing.

You can also use my gridfit code from the file exchange, which allows a choice of the smoothing parameter, thus the amount of smoothing.


John D'Errico

John D'Errico (view profile)

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