From: <Bill.Venables_at_csiro.au>

Date: Thu 26 Jan 2006 - 14:39:12 EST

Date: Thu 26 Jan 2006 - 14:39:12 EST

Yes Bert, this time you are missing something (unusually) ...

you have to write it as 1/sigma * dnorm((x - mu)/sigma). Here is a little example:

> D(Quote(pnorm((x-mu)/sigma)), "x")

dnorm((x - mu)/sigma) * (1/sigma)

> D(D(Quote(pnorm((x-mu)/sigma)), "x"), "mu")

(x - mu)/sigma * (dnorm((x - mu)/sigma) * (1/sigma)) * (1/sigma)

--- Like Brian, I recall the suggestion that we make D(...) extensible. I still think it is a good idea and worth considering. Under one scheme you would specify an object such as Fnorm <- structure(quote(pnorm(x, mu, sigma)), deriv = list(x = Quote(dnorm(x, mu, sigma)/sigms), mu = Quote(-dnorm(x, mu, sigma)/sigma), sigma = Quote(-(x - mu)*dnorm(x, mu, sigma)/sigma^2), class = "dfunction") ane write a generic "differentiate" function with a "dfunction" method and "D" as the default. I don't think it's quite that easy, but the plan is clear enough. Bill. -----Original Message----- From: r-help-bounces@stat.math.ethz.ch [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Berton Gunter Sent: Thursday, 26 January 2006 8:58 AM To: 'Spencer Graves'; r-help@stat.math.ethz.ch Subject: Re: [R] D(dnorm...)? dnorm() is an internal function, so I don't see how D (or deriv) can do anything with it symbolically. Am I missing something? -- BertReceived on Thu Jan 26 14:48:29 2006

> -----Original Message-----

> From: r-help-bounces@stat.math.ethz.ch> [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Spencer Graves> Sent: Wednesday, January 25, 2006 2:43 PM> To: r-help@stat.math.ethz.ch> Subject: [R] D(dnorm...)?>> Can someone help me understand the following:>> > D(expression(dnorm(x, mean)), "mean")> [1] 0> > sessionInfo()>> R version 2.2.1, 2005-12-20, i386-pc-mingw32>> attached base packages:> [1] "methods" "stats" "graphics" "grDevices" "utils"> "datasets"> [7] "base">> By my computations, this should be something like> ((mean-x)/sd^2)*dnorm(...).>> Thanks for your help.> Spencer Graves>> ______________________________________________> R-help@stat.math.ethz.ch mailing list> https://stat.ethz.ch/mailman/listinfo/r-help> PLEASE do read the posting guide!> http://www.R-project.org/posting-guide.html

> ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html

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