[Rd] deriv (PR#953)

[Peter Dalgaard BSA]

tlumley@u.washington.edu writes:

> The first bug is very strange and I suspect there's something going on in
> the memory management.  Supplying a function as the third argument should
> cause the body of the function to be replaced by the derivative. This
> sometimes works, but doesn't depend on the function in any simple way.
> 
> It seems to depend on how new the function is. With a new anonymous
> function it never works, but with a base function like lm or log it always
> works:
> 
>  ## works
>  deriv(expression(sin(cos(x) * y)), c("x","y"), log)
>  ## identical function
>  LOG<-function (x, base = exp(1))
>     if (missing(base)) .Internal(log(x)) else .Internal(log(x, base))
>  ## doesn't work
>  deriv(expression(sin(cos(x) * y)), c("x","y"), LOG)
> 
> Creating a new function somewhere else in the search path doesn't help
>  assign("a",function(x,y){},pos=3)
>  # doesn't work
>  deriv(expression(sin(cos(x) * y)), c("x","y"), a)
> 
> but copying a loaded function does
> 
>   library(tcltk)
>   a<-tkbind
>   #works
>   deriv(expression(sin(cos(x) * y)), c("x","y"), a)

<grin> 
You had me going there too.

Try stripping the "source" attribute from the template functions....
(or from the output of deriv() for that matter). I'll give it a think
how to do that inside the deriv function so as to preserve user
sanity.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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