Groups > comp.graphics.apps.gnuplot > #1395

Re: Fitting a function between two measurements

From	sfeam <sfeam@users.sourceforge.net>
Newsgroups	comp.graphics.apps.gnuplot
Subject	Re: Fitting a function between two measurements
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Date	Mon, 01 Oct 2012 20:36 -0700
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Voodjin wrote:

> Hi I have a little question and I'm not even sure if it's directly
> accesable through a gnuplot function. I have two different
> measurements (or better: their points) - let's call them true and
> false - in one single plot. What I now want is to plot a function
> which seperates the whole plot into two fields. One true-area and one
> false-area. What I've done up to now is to put some points by hand
> into the graph and then make a fit throught them (in the form f(x) =
> (a/(x-b))-c). However, this is obviously not very scientific as my eye
> isn't a very precise mathematical apparatus. So what I would like to
> have now is a way to tell Gnuplot: Find a good function which
> seperates both value-fields the best. Does something like this even
> exist?

It sounds like you are describing construction of a support vector
machine (SVM).  The Wikipedia page gives a good illustration.

  http://en.wikipedia.org/wiki/Support_vector_machine

Gnuplot does not implement SVM fitting, but you might try R.

	Ethan

> 
> I already thought it might be better to make a different plot with
> only those values which have many overlapping values from both fields
> and use them for a fit. Would this be a better attempt than the first
> one with putting some fitting points by hand?
> 
> Of course a "gnuplot, you do it"-function would be the best, but like
> already mentioned I don't have any idea if something like this exist.
> 
> I also appreciate responses which can guide me to some mathematical
> background that can tell me how good my approximation seems to be.
> 
> Thanks in advance!

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Thread

Fitting a function between two measurements Voodjin <rauhfaser@ymail.com> - 2012-09-30 15:48 -0700
  Re: Fitting a function between two measurements sfeam <sfeam@users.sourceforge.net> - 2012-10-01 20:36 -0700

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