Asked by John
on 21 Mar 2012

Hello,

I'm trying to use the kernal smoothing density function

http://www.mathworks.co.uk/help/toolbox/stats/ksdensity.html

What would the correct syntax be if I'm trying to smooth a vector x, with kernel epanechnikov with a width of 3?

Is it something like this?

[...] = ksdensity(x,kernel,epanechnikov,width, 3)

What would go on the right hand side of the equal sign?

Sincere thanks

John

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Answer by Peter Perkins
on 21 Mar 2012

John, all you are missing is quotes:

ksdensity(x,'kernel','epanechnikov','width',3)

BUT: you say, "if I'm trying to smooth a vector", which makes me think that maybe you're thinking that this is kernel smoothing, rather than kernel density estimation. KSDENSITY takes one vector containing a sample from some unknown distribution, and returns an estimate of the density of that distibution. Kernel smoothing, which KSDENSITY *doesn't* do, is a non-parametric regression method that takes two (or maybe more) vectors.

Hope this helps.

John
on 22 Mar 2012

Hi Peter,

Thank you for your reply and for pointing out that KSDENSITY cannot be used for smoothing.

I am trying to smooth two vectors. I have a recording of time (sec) and speed and I'm trying to smooth the curve.

Here is an example http://dl.dropbox.com/u/54057365/All/kernel.JPG

Is it possible to do this in Matlab?

Thank you

Kind Regards

John

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