Re: [Rd] extending the derivs table/fools rushing in

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Thu, 14 Aug 2008 15:47:38 -0400

You could see if Ryacas package can do what you want:

http://ryacas.googlecode.com

2008/8/14 Ben Bolker <bolker_at_zoology.ufl.edu>:
> Prof Brian Ripley wrote:
>> The derivative of plogis is surely dlogis. (And yes, there is a good
>> reason why we have such a function: take a look at its C code.)
>
> Doh.
>>
>> That means we would need an entry for dlogis too, I guess. I am not
>> convinced that there is a real need for these (and where does this
>> stop?) What would be much more useful is to make this user-extensible
>> (as Bill Venables pointed out a decade ago). [pd]norm were added in
>> 2002 to support MASS, the ability to do all of MASS in R being a goal at
>> the time.
>
> I agree it would be great to make this user-extensible, but it's
> probably a bit beyond me ... I found a web-reference of Venables saying
>
>> There is a detailed example towards the end of Ch. 9 of V&R on how
>> to extend D() and make.call(), which are the work horses for
>> deriv(), to handle new functions. The new functions handled there
>> are dnorm() and pnorm(), but I() would be even easier, of course.
>
> http://www.math.yorku.ca/Who/Faculty/Monette/pub/s-old/0690.html
>
> ... but this is from 1997 therefore presumably MASS3? or MASS2? --
> I can't find my copy of MASS3 at the moment, and don't own MASS2 ...
>
> The reason behind this is that I was trying to write a simple
> analytic derivative calculator for formulae of the form (e.g.)
>
> y ~ dbinom(prob=plogis(a+b*x),size=N)
>
> Obviously in this case I could just tell people to write the
> formula out as
>
> y ~ dbinom(prob=1/(1+exp(-(a+b*x))),size=N)
>
> ...
>
> Ben Bolker
>
>
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>



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