[R] D(dnorm...)?

[Spencer Graves]

Hi, Bert:

	  I think I was too terse:  Why didn't I get an error message?  When I 
tried the same thing with "dpois", I got an error message:

 > D(expression(dpois(x, prob)), "mean")
Error in D(expression(dpois(x, prob)), "mean") :
	Function 'dpois' is not in the derivatives table

	  With "dnorm", I got "0"!.  Whe didn't I get an error message?

	  Thanks for the reply.
	  Spencer Graves

Berton Gunter wrote:

> dnorm() is an internal function, so I don't see how D (or deriv) can do
> anything with it symbolically. Am I missing something?
> 
> -- Bert
>  
>  
> 
> 
>>-----Original Message-----
>>From: r-help-bounces at stat.math.ethz.ch 
>>[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Spencer Graves
>>Sent: Wednesday, January 25, 2006 2:43 PM
>>To: r-help at 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
>>
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> 
>