[R] Fitting a curve to to an oscillating scatter . .

[Prof Brian D Ripley]

On Sun, 13 Aug 2000, reza shahidzadeh mahani wrote:

> You can  get the lower frequency component nonparametrically by
> increasing the bandwidth (in kernel smoothing with ksmooth in S) or
> increasing penalty coefficient (in spline smoothing with smooth.spline in
> S).
> I don't know the corresponding function in R unfrotunately.

The same. But that is not what he asked for, and I was trying to answer the
actual question.

In scatter.smooth one uses `span' to set the amount of smoothing.

> 
> method) On Sun, 13 Aug 2000, Prof Brian D Ripley wrote:
> 
> > On Sun, 13 Aug 2000, Phil Rhoades wrote:
> > 
> > > I have just got going with R and think it is really nice however, as far as 
> > > I can see, it can't do what I got it for:
> > 
> > Sure it can.  It is a fully fledging computing language.
> > 
> > > I have some output from a computer simulation of mutating genes represented 
> > > by a biological statistic - so the graph looks roughly like the top of:
> > > 
> > > 	x = y^2
> > > 
> > > - with oscillations around the general curve.
> > > 
> > > If I use scatter.smooth() I get a nice curve representing the oscillations 
> > > but what the curve I want to fit is the more basic curve ie the top arm of 
> > > the x = y^2.
> > > 
> > > Any suggestions?
> > 
> > plot(x, y)
> > fit <- lm(y ~ I(x^0.5)) # or y ~ sqrt(x)
> > lines(predict(fit), sort(x))
> > 
> > if indeed the response is y to stimulus x.
> > 
> > 
> > -- 
> > Brian D. Ripley,                  ripley at stats.ox.ac.uk
> > Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> > University of Oxford,             Tel:  +44 1865 272861 (self)
> > 1 South Parks Road,                     +44 1865 272860 (secr)
> > Oxford OX1 3TG, UK                Fax:  +44 1865 272595
> > 
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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