Re: [R] help in density estimation
On 23/09/2010 11:42 AM, wangguojie2006 wrote: b-runif(1000,0,1) f-density(b) f is a list of things, including x values where the density is computed, and y values for the density there. So you could do it by linear interpolation using approx or approxfun. For example b - runif(1000,0,1) flist - density(b) f - approxfun(flist$x, flist$y) f(0.2) [1] 0.9717893 f(-1) [1] NA If you don't like the NA for an out-of-range argument, then choose something different from the default for the rule argument to approxfun. Duncan Murdoch __ 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.
Re: [R] help in density estimation
On 23-Sep-10 16:52:09, Duncan Murdoch wrote: On 23/09/2010 11:42 AM, wangguojie2006 wrote: b-runif(1000,0,1) f-density(b) f is a list of things, including x values where the density is computed, and y values for the density there. So you could do it by linear interpolation using approx or approxfun. For example b - runif(1000,0,1) flist - density(b) f - approxfun(flist$x, flist$y) f(0.2) [1] 0.9717893 f(-1) [1] NA If you don't like the NA for an out-of-range argument, then choose something different from the default for the rule argument to approxfun. Duncan Murdoch Or, perhaps more transparently (and more explicitly modifiable): b-runif(1000,0,1) f - density(b, from=0, to=1, n=512) plot(f$x, f$y, type=l, col=blue, xlim=c(0,1), ylim=c(0,1.5)) ## Plot the density estimate x0 - 0.5## Target value of x i0 - max(which(f$x = x0)) i1 - min(which(f$x x0)) u0 - f$x[i0] ; v0 - f$y[i1] u1 - f$x[i1] ; v1 - f$y[i1] y0 - v0 + (v1-v0)*(x0-u0)/(u1-u0) ## Linear interpolation points(x0, y0, pch=+, col=red) ## Add interpolated point Ted. E-Mail: (Ted Harding) ted.hard...@manchester.ac.uk Fax-to-email: +44 (0)870 094 0861 Date: 23-Sep-10 Time: 18:05:41 -- XFMail -- __ 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.
Re: [R] help in density estimation
You could do: b - runif(1, 0, 1) tmp - density(b, from=0.5, to=0.5, n=1) tmp$y As one direct approach. You could also look at the logspline package for an alternative for density estimation that provides you with a density function (and also allows for finite domains). -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 -Original Message- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- project.org] On Behalf Of wangguojie2006 Sent: Thursday, September 23, 2010 9:43 AM To: r-help@r-project.org Subject: [R] help in density estimation Hi, guys, I'm using kernel density estimation. But how can I return to a density estimation for a fixed point? For example, b-runif(1000,0,1) f-density(b) How can I get the value of density(b) at b=0.5? Your help is extremely appreciated. Thanks. Jay -- View this message in context: http://r.789695.n4.nabble.com/help-in- density-estimation-tp2552264p2552264.html Sent from the R help mailing list archive at Nabble.com. __ 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. __ 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.
Re: [R] help in density estimation
You guys are really good. Thanks. -- View this message in context: http://r.789695.n4.nabble.com/help-in-density-estimation-tp2552264p2552484.html Sent from the R help mailing list archive at Nabble.com. __ 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.
Re: [R] help in density estimation
There was a typo error in my code below. See the inserted correction. On 23-Sep-10 17:05:45, Ted Harding wrote: On 23-Sep-10 16:52:09, Duncan Murdoch wrote: On 23/09/2010 11:42 AM, wangguojie2006 wrote: b-runif(1000,0,1) f-density(b) f is a list of things, including x values where the density is computed, and y values for the density there. So you could do it by linear interpolation using approx or approxfun. For example b - runif(1000,0,1) flist - density(b) f - approxfun(flist$x, flist$y) f(0.2) [1] 0.9717893 f(-1) [1] NA If you don't like the NA for an out-of-range argument, then choose something different from the default for the rule argument to approxfun. Duncan Murdoch Or, perhaps more transparently (and more explicitly modifiable): b-runif(1000,0,1) f - density(b, from=0, to=1, n=512) plot(f$x, f$y, type=l, col=blue, xlim=c(0,1), ylim=c(0,1.5)) ## Plot the density estimate x0 - 0.5## Target value of x i0 - max(which(f$x = x0)) i1 - min(which(f$x x0)) ##u0 - f$x[i0] ; v0 - f$y[i1]## WRONG! u0 - f$x[i0] ; v0 - f$y[i0]## Correction u1 - f$x[i1] ; v1 - f$y[i1] y0 - v0 + (v1-v0)*(x0-u0)/(u1-u0) ## Linear interpolation points(x0, y0, pch=+, col=red) ## Add interpolated point Ted. E-Mail: (Ted Harding) ted.hard...@manchester.ac.uk Fax-to-email: +44 (0)870 094 0861 Date: 23-Sep-10 Time: 18:05:41 -- XFMail -- E-Mail: (Ted Harding) ted.hard...@manchester.ac.uk Fax-to-email: +44 (0)870 094 0861 Date: 23-Sep-10 Time: 20:38:53 -- XFMail -- __ 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.
