On 7/29/2008 7:55 AM, Oehler, Friderike (AGPP) wrote:
Dear Rusers,
I am still an unexperienced builder of functions and loops, so my question is
very basic: Is it possible to introduce a second variable (j) into my loop.
To examplify:
# This works fine:
fn <- function (x) {if (x>46 & x<52) 1 else 0}
res <-NULL
for (i in 40:60) res <-c(res,fn(i))
res
# But here, there is an error in the "for" expression:
fn <- function (x,y) {if (x>46 & x<52 & y<12) 1 else 0 }
res <-NULL
for (i in 40:60 & j in 0:20) res <-c(res,fn(i,j))
# How do I have to write the expression "i in 40:60 & j in 0:20"? Or is there
no way to do that, i.e. I have to do the calculation in two steps?
You need two steps. You probably want either
for (i in 40:60) for (j in 0:20) res <-c(res,fn(i,j))
or
i <- 40:60
j <- 0:20
for (ind in seq_along(i)) res <- c(res, fn(i[ind], j[ind]))
(which do quite different loops).
Duncan Murdoch
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