[R] keep the row indexes/names when do aggregate

2008-09-24 Thread zhihuali 

Hi, R-users,

If I have a data frame like this:
x-data.frame(g=c(g1,g2,g1,g1,g2),v=c(1,7,3,2,8))
   g v
1 g1 1
2 g2 7
3 g1 3
4 g1 2
5 g2 8


It contains two groups, g1 and g2. Now for each group I want the max v:

 aggregate(x$v,list(g=x$g),max)
   g x
1 g1 3
2 g2 8

Beautiful. But what if I want to keep the row index of (g1 3) and (g2 8) in the 
original x? 
So I want is:
do something
   g x
 3 g1 3
 5 g2 8

Of course it'd may make much more sense if the row indexes are some row names 
that I want to keep.

Is there a simple way to do that?

Thanks a lot!

Z


 


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Re: [R] keep the row indexes/names when do aggregate

2008-09-24 Thread Gabor Grothendieck 
Rather than aggregate, use order and duplicated as in this post:

https://stat.ethz.ch/pipermail/r-help/2008-September/173139.html

On Wed, Sep 24, 2008 at 11:21 AM, zhihuali [EMAIL PROTECTED] wrote:

 Hi, R-users,

 If I have a data frame like this:
x-data.frame(g=c(g1,g2,g1,g1,g2),v=c(1,7,3,2,8))
   g v
 1 g1 1
 2 g2 7
 3 g1 3
 4 g1 2
 5 g2 8


 It contains two groups, g1 and g2. Now for each group I want the max v:

 aggregate(x$v,list(g=x$g),max)
   g x
 1 g1 3
 2 g2 8

 Beautiful. But what if I want to keep the row index of (g1 3) and (g2 8) in 
 the original x?
 So I want is:
do something
   g x
  3 g1 3
  5 g2 8

 Of course it'd may make much more sense if the row indexes are some row names 
 that I want to keep.

 Is there a simple way to do that?

 Thanks a lot!

 Z





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 [[elided Hotmail spam]]

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 __
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 https://stat.ethz.ch/mailman/listinfo/r-help
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 and provide commented, minimal, self-contained, reproducible code.


__
R-help@r-project.org mailing list
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and provide commented, minimal, self-contained, reproducible code.

Re: [R] keep the row indexes/names when do aggregate

2008-09-24 Thread Adaikalavan Ramasamy 

Not the most elegant solution but here goes.

   df - data.frame(g=c(g1,g2,g1,g1,g2),v=c(1,7,3,2,8))

   rownames.which.max - function(m, col){
  w - which.max( m[ , col] )
  return( rownames(m)[w] )
   }

   df.split - split(df, df$g)
   ws - sapply( df.split, rownames.which.max, col=v )

   ws
g1  g2
   3 5

   df[ws, ]
  g v
   3 g1 3
   5 g2 8

Regards, Adai

zhihuali wrote:

Hi, R-users,

If I have a data frame like this:

x-data.frame(g=c(g1,g2,g1,g1,g2),v=c(1,7,3,2,8))

   g v
1 g1 1
2 g2 7
3 g1 3
4 g1 2
5 g2 8


It contains two groups, g1 and g2. Now for each group I want the max v:


aggregate(x$v,list(g=x$g),max)

   g x
1 g1 3
2 g2 8

Beautiful. But what if I want to keep the row index of (g1 3) and (g2 8) in the original x? 
So I want is:

do something

   g x
 3 g1 3
 5 g2 8

Of course it'd may make much more sense if the row indexes are some row names 
that I want to keep.

Is there a simple way to do that?

Thanks a lot!

Z


 



_
[[elided Hotmail spam]]

[[alternative HTML version deleted]]

__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.


__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.