[R] density at particular values

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Shant Ch
> Sent: Saturday, November 20, 2010 6:34 PM
> To: David Winsemius
> Cc: r-help at r-project.org
> Subject: Re: [R] density at particular values
> 
> 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.

print(density(x)) displays a 6-number summary of the
x and y outputs of density, which are only tangentially
related to the data.  (The default x output is a evenly
spaced seqence of n=512 values covering the range of
the input x.)  I don't know why this display was chosen.
 
> 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.

If you really just want the density at a single
point, x0 (=1 in your case), you can do
   d0 <- density(x, from=x0, to=x0, n=1)$y
(density only lets you choose the output x vector
as an evenly spaced sequence parameterized by
from, to, and n.)

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> 
> Shant
>  
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> 
> ________________________________
> From: David Winsemius <dwinsemius at comcast.net>
> 
> Cc: r-help at 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 at 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]]
> 
> ______________________________________________
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> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
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>