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Hao Cen

2009-Nov-16 19:42 UTC

[R] extracting the last row of each group in a data frame

Hi,

I would like to extract the last row of each group in a data frame.

The data frame is as follows

Name Value
A 1
A 2
A 3
B 4
B 8
C 2
D 3

I would like to get a data frame as
Name Value
A 3
B 8
C 2
D 3

Thank you for your suggestions in advance

Jeff

baptiste auguie

2009-Nov-16 19:51 UTC

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[R] extracting the last row of each group in a data frame

Hi,

You could try plyr,

library(plyr)

ddply(d,.(Name), tail,1)

  Name Value
1    A     3
2    B     8
3    C     2
4    D     3

HTH,

baptiste

2009/11/16 Hao Cen <hcen at andrew.cmu.edu>:> Hi,
>
> I would like to extract the last row of each group in a data frame.
>
> The data frame is as follows
>
> Name Value
> A 1
> A 2
> A 3
> B 4
> B 8
> C 2
> D 3
>
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
>
> Thank you for your suggestions in advance
>
> Jeff
>
> ______________________________________________
> R-help at 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.
>

Jorge Ivan Velez

2009-Nov-16 19:52 UTC

head link

[R] extracting the last row of each group in a data frame

Dear Jeff,

Here is a suggestion using tapply:

data.frame(last = with(x, tapply(Value, Name, function(x) x[length(x)])))

See ?tapply for more information.

HTH,
Jorge


On Mon, Nov 16, 2009 at 2:42 PM, Hao Cen <> wrote:
> Hi,
>
> I would like to extract the last row of each group in a data frame.
>
> The data frame is as follows
>
> Name Value
> A 1
> A 2
> A 3
> B 4
> B 8
> C 2
> D 3
>
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
>
> Thank you for your suggestions in advance
>
> Jeff
>
> ______________________________________________
> 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.
>
	[[alternative HTML version deleted]]

David Winsemius

2009-Nov-16 19:53 UTC

head link

[R] extracting the last row of each group in a data frame

On Nov 16, 2009, at 2:42 PM, Hao Cen wrote:
> Hi,
>
> I would like to extract the last row of each group in a data frame.
>
> The data frame is as follows
>
> Name Value
> A 1
> A 2
> A 3
> B 4
> B 8
> C 2
> D 3
>
by(dfname$Value, dfname$Name, tail, 1) #which gets you a list

Or:

aggregate(dfname$Value, list(dfname$Name), tail, 1)  #which returns a  
data.frame
   Group.1 x
1       A 3
2       B 8
3       C 2
4       D 3
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
>
-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

cls59

2009-Nov-16 19:57 UTC

head link

[R] extracting the last row of each group in a data frame

jeffc wrote:> 
> Hi,
> 
> I would like to extract the last row of each group in a data frame.
> 
> The data frame is as follows
> 
> Name Value
> A 1
> A 2
> A 3
> B 4
> B 8
> C 2
> D 3
> 
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
> 
> Thank you for your suggestions in advance
> 
> Jeff
> 
Try using the base function by() or ddply() from Hadley Wickham's plyr
package:

  require( plyr )

  tstData <- structure(list(Name = structure(c(1L, 1L, 1L, 2L, 2L, 3L, 4L),
.Label = c("A", 
"B", "C", "D"), class = "factor"), Value
= c(1L, 2L, 3L, 4L,
8L, 2L, 3L)), .Names = c("Name", "Value"), class =
"data.frame", row.names c(NA,
-7L))

  lastRows <- ddply( tstData, 'Name', function( group ){

    return(
      data.frame( Value = tail( group[['Value']], n = 1 ) )
    )

  })

  lastRows
    Name Value
  1    A     3
  2    B     8
  3    C     2
  4    D     3


Hope this helps!


-Charlie


-----
Charlie Sharpsteen
Undergraduate
Environmental Resources Engineering
Humboldt State University
-- 
View this message in context:
http://old.nabble.com/extracting-the-last-row-of-each-group-in-a-data-frame-tp26378194p26378404.html
Sent from the R help mailing list archive at Nabble.com.

Peter Ehlers

2009-Nov-16 20:16 UTC

head link

[R] extracting the last row of each group in a data frame

I would use pkg:plyr, but just to show how
versatile R is:

ind <- cumsum(rle(as.numeric(dat$Name))$lengths)
dat[ind, ]

where I'm assuming that your data frame is
called 'dat'.

  -Peter Ehlers

Hao Cen wrote:> Hi,
> 
> I would like to extract the last row of each group in a data frame.
> 
> The data frame is as follows
> 
> Name Value
> A 1
> A 2
> A 3
> B 4
> B 8
> C 2
> D 3
> 
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
> 
> Thank you for your suggestions in advance
> 
> Jeff
> 
> ______________________________________________
> R-help at 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.
> 
>

Gabor Grothendieck

2009-Nov-16 23:27 UTC

head link

[R] extracting the last row of each group in a data frame

Try this:
> aggregate(DF[-1], DF[1], tail, 1)  Name Value
1    A     3
2    B     8
3    C     2
4    D     3


On Mon, Nov 16, 2009 at 2:42 PM, Hao Cen <hcen at andrew.cmu.edu>
wrote:> Hi,
>
> I would like to extract the last row of each group in a data frame.
>
> The data frame is as follows
>
> Name Value
> A 1
> A 2
> A 3
> B 4
> B 8
> C 2
> D 3
>
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
>
> Thank you for your suggestions in advance
>
> Jeff
>
> ______________________________________________
> R-help at 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.
>

Hao Cen

2009-Nov-17 04:06 UTC

head link

[R] extracting the last row of each group in a data frame

Thanks to all who helped. These are all great suggestions. 

Jeff

-----Original Message-----
From: Gabor Grothendieck [mailto:ggrothendieck at gmail.com] 
Sent: Monday, November 16, 2009 6:27 PM
To: Hao Cen
Cc: r-help at r-project.org
Subject: Re: [R] extracting the last row of each group in a data frame

Try this:
> aggregate(DF[-1], DF[1], tail, 1)  Name Value
1    A     3
2    B     8
3    C     2
4    D     3


On Mon, Nov 16, 2009 at 2:42 PM, Hao Cen <hcen at andrew.cmu.edu>
wrote:> Hi,
>
> I would like to extract the last row of each group in a data frame.
>
> The data frame is as follows
>
> Name Value
> A 1
> A 2
> A 3
> B 4
> B 8
> C 2
> D 3
>
> I would like to get a data frame as
> Name Value
> A 3
> B 8
> C 2
> D 3
>
> Thank you for your suggestions in advance
>
> Jeff
>
> ______________________________________________
> R-help at 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.
>

Nutter, Benjamin

2009-Nov-17 13:04 UTC

head link

[R] extracting the last row of each group in a data frame

I usually use the following function:

last.record <- function(data, id, ..., na.last=TRUE, decreasing=FALSE){

  #*** Make vector of variables to sort by
  v <- c(id, unlist(list(...)))

  #*** Sort Data Frame
  data <- data[do.call(order,
            c(data[,v, drop=FALSE], na.last=na.last,
decreasing=decreasing)),]

  #*** Extract last record for each id
  data[!duplicated(data[,id], fromLast=TRUE),]
}


Data        Data Frame from which the record is to be extracted
Id          ID variable from which the record is to be extracted.  The
data frame is automatically
	      sorted by this variable.  May be either a character string
or an integer.
...         Names of variables (or indices) in additon to id by which
data should be sorted.
na.last     Argument passed to order().  Determines if missing values
are placed at the end
	      of the sorting.
Decreasing  Argument passed to order().  Determines if data frame is
sorted in descending
	      order.



So, in your example
> df <- data.frame(Name = c("A", "A", "A",
"B", "B", "C", "D"),                   Value = c(1, 2, 3, 4, 8, 2, 3))

> last.record(df, "Name", "Value")
> last.record(df, 1, 2)
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Hao Cen
Sent: Monday, November 16, 2009 2:43 PM
To: r-help at r-project.org
Subject: [R] extracting the last row of each group in a data frame

Hi,

I would like to extract the last row of each group in a data frame.

The data frame is as follows

Name Value
A 1
A 2
A 3
B 4
B 8
C 2
D 3

I would like to get a data frame as
Name Value
A 3
B 8
C 2
D 3

Thank you for your suggestions in advance

Jeff

______________________________________________
R-help at 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.


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