From: Spencer Graves <spencer.graves_at_pdf.com>

Date: Thu 26 Jan 2006 - 15:14:07 EST

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

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

*> R-help@stat.math.ethz.ch mailing list
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*> https://stat.ethz.ch/mailman/listinfo/r-help
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*> PLEASE do read the posting guide!
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*> http://www.R-project.org/posting-guide.html
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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 Received on Thu Jan 26 15:20:36 2006

Date: Thu 26 Jan 2006 - 15:14:07 EST

Hello, Bill:

I'm not qualified to make this suggestion since I'm incapable of turning it into reality, but what about creating a link between R and one of the Mathematica clones like Yacas? I can immagine that it could be substantially more difficult than linking R to other software like Excel, but ... .

Spencer Graves

Bill.Venables@csiro.au wrote:

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

*>
**> As Brian Ripley pointed out 'dnorm' is in the derivative table, *but*
**> only as a function of one variable. So if you want to find the
**> derivative of
**>
**> dnorm(x, mean, sigma)
**>
**> you have to write it as 1/sigma * dnorm((x - mu)/sigma). Here is a
**> little example:
**>
**>
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>>D(Quote(pnorm((x-mu)/sigma)), "x")

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

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

>>-----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 Received on Thu Jan 26 15:20:36 2006

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