R help - May 2005 - functions of functions

Hi

I have an application where my difficulty boils down to not
being able to define a function f() with the following properties:

f("sin",0:2,x)               #returns sin(x+0) + sin(x+1) + sin(x+2)
f(c("sin","cos"), 1:2,x)     #returns sin(x+1) + cos(x+2)
f(c("sin","cos","exp"),3,x)  #returns sin(x+3) +
cos(x+3) + exp(x+3)

anyone?


--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743

Robin Hankin wrote:
> Hi
> 
> I have an application where my difficulty boils down to not
> being able to define a function f() with the following properties:
> 
> f("sin",0:2,x)               #returns sin(x+0) + sin(x+1) +
sin(x+2)
> f(c("sin","cos"), 1:2,x)     #returns sin(x+1) +
cos(x+2)
> f(c("sin","cos","exp"),3,x)  #returns
sin(x+3) + cos(x+3) + exp(x+3)
> 
> anyone?
Not really nice, but hopefully works:

f <- function(foo, int, x){
   # too lazy to think myself about recycling:
   X <- cbind(foo, x + int)
   # mapply-ing over both columns
   values <- mapply(function(foo, x) do.call(foo, list(x)),
        X[,1], as.integer(X[,2]))
   # caculating the sum:
   return(sum(values))
}


Uwe



> 
> -- 
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
>  tel  023-8059-7743
> 
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