You could see if Ryacas package can do what you want: http://ryacas.googlecode.com
2008/8/14 Ben Bolker <[EMAIL PROTECTED]>: > 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 > > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
