> -----Original Message-----
> From: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] On Behalf Of bsm2
> Sent: 23 January 2013 20:00
> To: r-help@r-project.org
> Subject: [R] Pasting a list of parameters into a function
>
> I need to repeat a function many times, with differing
> parameters held constant across iterations. To accomplish
> this, I would like to create a list (or vector) of
> parameters, and then insert that list into the function.
>
> For example:
>
> q<-("l,a,b,s")
This isn't a ist, it's a single quoted string. A list would be
q <- list(l=<value>,a=<value>, b=<value>, s=<value> )
(with common sense replacement of <value> with the values you want to pass
> genericfunction<-function(q){
> }
That'll work, assuming your function dereferences q, for example using q$l or,
perhaps, using with()
Other things might work too though. For example, assuming each item is
single-valued numeric, set up a matrix with columns l, a, b, s or or data frame
(say d) with variables l, a, b, s, then use
apply(d, 1, genericfunction) #iterate over rows, coercing each row to vector
with g using either the numeric indices (like q[1], q[2]) or, for the data
frame version, the names (q['a'] etc) because in the data frame version q will
be a named vector.
You could also construct a list of lists, and use lapply or sapply to do the
iteration over the whole list; that would work whatever type l, a, b, s are.
Example:
param.sets <- list(
list(l=1,a='a', b=2.3, s=TRUE ),
list(l=5,a='p', b=7.5, s=FALSE ),
list(l=3,a='r', b=2.5, s=TRUE )
)
a.function <- function(q) with(q, paste(l, a, b, s) )
sapply(param.sets, a.function)
You could also use mapply and supply l, a etc as individual vectors, factors
etc, but that would need a different function definition:
d <- data.frame(l=1:6, a=gl(3,2, labels=letters[1:3]), b=6:1, s=rnorm(6)) #to
package them neatly
mfun <- function(l, a, b, s) paste(l, a, b, s)
#Then
with(d, mapply(mfun, l, a, b, s))
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