Hi Shant,
You could use approxfun() on the density as follows:
> # data
> set.seed(123)
> x <- c(rnorm(40,5,3),rcauchy(30,0,4),rexp(30,6))
> d <- density(x)
> str(d)
List of 7
$ x : num [1:512] -115 -115 -115 -114 -114 ...
$ y : num [1:512] 3.24e-05 6.99e-05 1.40e-04 2.58e-04 4.43e-04 ...
$ bw : num 1.62
$ n : int 100
$ call : language density.default(x = x)
$ data.name: chr "x"
$ has.na : logi FALSE
- attr(*, "class")= chr "density"
>
> # showing values around x = 1
> # here, "y" is the density
> with(d, cbind(x, y))[d$x > 0 & d$x < 1.5,]
x y
[1,] 0.3489268 0.1084530
[2,] 0.8031464 0.1070246
[3,] 1.2573661 0.1015048
>
> # function to estimate the density at x0
> f <- with(d, approxfun(x, y))
>
> # estimating f at x0 = 1
> f(1)
[1] 0.1046324
HTH,
Jorge
On Sat, Nov 20, 2010 at 9:34 PM, Shant Ch <> wrote:
> David, I did look at ?density many times. I think I didn't explain what I
> have
> to find.
>
> Suppose I have a data.
> x<- c(rnorm(40,5,3),rcauchy(30,0,4),rexp(30,6))
>
> Suppose I don't have information about the mixture, I have been given only
> the
> data.
>
> density(x) will give the 6 number summary of the data, given as x and also
> the 6
> number summary of the density of density given as y.
>
> I want to find the density of the given data at x=1. I basically want the
> value
> of y(=density) for x=1 i.e. kernel density at x=1.
>
> Shant
>
>
>
>
>
>
>
>
>
>
>
>
>
> ________________________________
> From: David Winsemius <dwinsem...@comcast.net>
>
> Cc: r-help@r-project.org
> Sent: Sat, November 20, 2010 8:54:32 PM
> Subject: Re: [R] density at particular values
>
>
> On Nov 20, 2010, at 8:07 PM, Shant Ch wrote:
>
> > Hello everyone!
> >
> > I want to use density function of R to compute the density at x(=0, say).
> But
> >it
> > is giving me the 5-number summary and mean of the data and densities at
> that
> > point.
> > I just want the densities at different values specified by me. Can anyone
> let
> >me
> > know how can I find that?
>
> Here's what you should have done (even before posting):
>
> ?density
> <Read the help page to see the structure of what density() returns.>
> "Value
> x the n coordinates of the points where the density is estimated.
>
> y the estimated density values. These will be non-negative, but can be
> zero."
>
> Realize that the "specified by me" part is either going to be modified to
> "pick
> an existing estimate near my specification" or that you will need to
> approximate
> the value. So what is the actual problem (and the actual data setup) ?
>
> --David.
>
>
> >
> > For example
> >
> >
> > Thanks in advance for your help.
> >
> >
> > Shant
> >
> >
> >
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius, MD
> West Hartford, CT
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
[[alternative HTML version deleted]]
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and provide commented, minimal, self-contained, reproducible code.
