R> DF <- data.frame(x = rnorm(40000), y = rnorm(40000))
R> foo <- function(z, x, y) z[x] + z[y]
R> bar <- function(x, y) x + y
R> system.time(x <- apply(DF, 1, foo, x = "x", y = "y"))
[1] 6.94 0.04 7.37 NA NA
R> system.time(y <- with(DF, bar(x, y))) # from A. Liaw
[1] 0.01 0.00 0.01 NA NA
R> all(x == y)
[1] TRUE
R> system.time(z <- mapply("bar", DF[,1], DF[,2]))Timing stopped at: 145.49 0.26 156.74 NA NA R> # not sure why mapply doesn't work here...
Best, Sundar
Ramzi Feghali wrote:
Another another neat way is:
DF <- data.frame(x=1:4, y=rep(1,4)) foo <- function(z,x,y)z[x]+z[y] apply(DF,1,foo,x="x",y="y")
1 2 3 4 2 3 4 5 or
DF <- data.frame(x=1:4, y=rep(1,4)) foo <- function(z)z<-x+y foo(DF)
[1] 2 3 4 5
"Liaw, Andy" <[EMAIL PROTECTED]> wrote: Another neat way is:
with(DF, foo(x, w))
HTH, Andy
-----Original Message----- From: peter leonard [mailto:[EMAIL PROTECTED] Sent: Sunday, June 08, 2003 4:35 PM To: [EMAIL PROTECTED] Subject: [R] Basic question on applying a function to each row of a dataframe
Hi,
I have a function foo(x,y) and a dataframe, DF, comprised of two vectors, x & w, as follows :
x w 1 1 1 2 2 1 3 3 1 4 4 1
etc
I would like to apply the function foo to each 'pair' within DF e.g foo(1,1), foo(2,1), foo(3,1) etc
I have tried
apply(DF,foo) apply(DF[,],foo) apply(DF[DF$x,DF$w],foo)
However, none of the above worked. Can anyone help ?
Thanks in advance, Peter
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