R help - Jun 2003 - 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

How about the following:

 > DF <- data.frame(x=1:4, y=rep(1,4))
 > foo <- function(x, y)x+y
 > foo(DF$x, DF$y)
[1] 2 3 4 5

hth.  spencer graves

peter leonard wrote:
> 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
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

Hi,

You need to tell the apply() whether you want to apply the function to 
rows (1) or columns (2).

So in your case you may want to try something like:
  apply(DF, 1, foo)

On Sun, 8 Jun 2003, peter leonard wrote:
> 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)
> 
-- 
Cheers,

Kevin

------------------------------------------------------------------------------
"On two occasions, I have been asked [by members of Parliament],
'Pray, Mr. Babbage, if you put into the machine wrong figures, will
the right answers come out?' I am not able to rightly apprehend the
kind of confusion of ideas that could provoke such a question."

-- Charles Babbage (1791-1871) 
---- From Computer Stupidities: http://rinkworks.com/stupid/

--
Ko-Kang Kevin Wang
Master of Science (MSc) Student
SLC Tutor and Lab Demonstrator
Department of Statistics
University of Auckland
New Zealand
Homepage: http://www.stat.auckland.ac.nz/~kwan022
Ph: 373-7599
    x88475 (City)
    x88480 (Tamaki)

Hi Keven,
This returns :

Error in FUN(newX[, i], ...) : Argument "y" is missing, with no
default


E.g
>x<-c(1,2,3,4)
>w<-c(1,1,1,1)
>DF<-data.frame(x,w)
>foo <- function(x, y)x+y apply(DF, 1, foo)
Error in FUN(newX[, i], ...) : Argument "y" is missing, with no
default

Regards
Peter




>From: Ko-Kang Kevin Wang <kwan022 at stat.auckland.ac.nz>
>To: peter leonard <pfleonard at hotmail.com>
>CC: r-help at stat.math.ethz.ch
>Subject: Re: [R] Basic question on applying a function to each row of a 
>dataframe Date: Mon, 9 Jun 2003 08:54:02 +1200 (NZST)
>
>Hi,
>
>You need to tell the apply() whether you want to apply the function to
>rows (1) or columns (2).
>
>So in your case you may want to try something like:
>   apply(DF, 1, foo)
>
>On Sun, 8 Jun 2003, peter leonard wrote:
>
> > 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)
> >
>
>--
>Cheers,
>
>Kevin
>
>------------------------------------------------------------------------------
>"On two occasions, I have been asked [by members of Parliament],
>'Pray, Mr. Babbage, if you put into the machine wrong figures, will
>the right answers come out?' I am not able to rightly apprehend the
>kind of confusion of ideas that could provoke such a question."
>
>-- Charles Babbage (1791-1871)
>---- From Computer Stupidities: http://rinkworks.com/stupid/
>
>--
>Ko-Kang Kevin Wang
>Master of Science (MSc) Student
>SLC Tutor and Lab Demonstrator
>Department of Statistics
>University of Auckland
>New Zealand
>Homepage: http://www.stat.auckland.ac.nz/~kwan022
>Ph: 373-7599
>     x88475 (City)
>     x88480 (Tamaki)
>
>

This works fine.
Thanks
Peter

>From: Spencer Graves <spencer.graves at PDF.COM>
>To: peter leonard <pfleonard at hotmail.com>
>CC: r-help at stat.math.ethz.ch
>Subject: Re: [R] Basic question on applying a function to each row of 
>a	dataframe
>Date: Sun, 08 Jun 2003 13:48:04 -0700
>
>How about the following:
>
> > DF <- data.frame(x=1:4, y=rep(1,4))
> > foo <- function(x, y)x+y
> > foo(DF$x, DF$y)
>[1] 2 3 4 5
>
>hth.  spencer graves
>
>peter leonard wrote:
>>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
>>
>>______________________________________________
>>R-help at stat.math.ethz.ch mailing list
>>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>
>

On Sun, 8 Jun 2003, peter leonard wrote:
> 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
>
In R 1.7.0 there is a function mapply() for this sort of thing.

mapply("foo",DF[,1],DF[,2])

	-thomas

This works fine. Thanks everybody for all your help,

Peter


>From: Thomas Lumley <tlumley at u.washington.edu>
>To: peter leonard <pfleonard at hotmail.com>
>CC: r-help at stat.math.ethz.ch
>Subject: Re: [R] Basic question on applying a function to each row of a 
>dataframe Date: Mon, 9 Jun 2003 06:47:20 -0700 (PDT)
>
>On Sun, 8 Jun 2003, peter leonard wrote:
>
> > 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
> >
>
>In R 1.7.0 there is a function mapply() for this sort of thing.
>
>mapply("foo",DF[,1],DF[,2])
>
>	-thomas
>