Hello Uwe

thanks for this.   Unfortunately it doesn't quite do what I want:


R> x <- c(0.3,0.3,0.5) R> f(c("sin","cos"),1:2,x)


1] 1.266795 Warning messages: 1: longer object length is not a multiple of shorter object length in: x + int 2: number of rows of result is not a multiple of vector length (arg 1) in: cbind(foo, x + int) R>


[


I need

R> sin(x+1) + cos(x+2)
[1] 0.2972822 0.2972822 0.1963514

]


best wishes

Robin



On May 9, 2005, at 08:34 am, Uwe Ligges wrote:

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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