[R] functions and strings

[Peter Dalgaard]

Robin Hankin <r.hankin at noc.soton.ac.uk> writes:

> Rich
> 
> that is sweeeeeeeeeeeeet
> 
> and does exactly what I want.
> 
> Thank you very much.


I just wonder whatever substitute() did to get ignored like that?

> substitute(1 + sin(cos(x)) + exp(x^2), list(x=quote(xyz)))
1 + sin(cos(xyz)) + exp(xyz^2)

 
> 
> best wishes
> 
> rksh
> 
> On 13 Sep 2006, at 10:54, Rich FitzJohn wrote:
> 
> > Hi,
> >
> > Perhaps try this (based on 'bquote'):
> >
> > rewrite.expression <- function(expr, to, dep) {
> >   f <- function(expr) {
> >     if ( length(expr) == 1 )
> >       if ( expr == as.name(dep) )
> >         as.name(to)
> >       else
> >         expr
> >     else
> >       as.call(lapply(expr, f))
> >   }
> >   f(expr)
> > }
> >
> > rewrite <- function(expr, to, dep='x') {
> >   rewrite.expression(substitute(expr), to, dep)
> > }
> >
> >> rewrite(1 + sin(cos(x)) + exp(x^2), 'xyz')
> > 1 + sin(cos(xyz)) + exp(xyz^2)
> >> rewrite(sin(x)+exp(x), 'xyz')
> > sin(xyz) + exp(xyz)
> >> rewrite(sin(i) + cos(sin(i^2)), 'tti', 'i')
> > sin(tti) + cos(sin(tti^2))
> > ## Or, closer to your example, using the name of the argument and body
> > ## of the function:
> > f <- function(r)
> >   2*r/sin(r) - b
> >
> >> rewrite.expression(body(f), 'foo', names(formals(f)))
> > 2 * foo/sin(foo) - b
> >
> > Hope that helps,
> > Rich
> >
> 
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
>   tel  023-8059-7743
> 
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> 

-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907