RE: [R] Basic question on applying a function to each row of a dataframe

2003-06-09 Thread Ramzi Feghali 
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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Re: [R] Basic question on applying a function to each row of a dataframe

2003-06-09 Thread Sundar Dorai-Raj 
Yes, but very slow for this example when the data.frame gets large

R DF - data.frame(x = rnorm(4), y = rnorm(4))
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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Re: [R] Basic question on applying a function to each row of a dataframe

2003-06-09 Thread Thomas Lumley 
On Mon, 9 Jun 2003, Sundar Dorai-Raj wrote:

 Yes, but very slow for this example when the data.frame gets large

Indeed. However, it works when the function is not already vectorised, and
if the function is already vectorised it is unnecessary.


-thomas

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