Or with plyr:
R> library(plyr)
R> ans <- ddply(x, .(Date), function(df) df[which.max(df$Time),])
-steve
On Wed, Aug 14, 2013 at 2:18 PM, Steve Lianoglou
<lianoglou.st...@gene.com> wrote:
> While we're playing code golf, likely faster still could be to use
> data.table. Assume your data is in a data.frame named "x":
>
> R> library(data.table)
> R> x <- data.table(x, key=c('Date', 'Time'))
> R> ans <- x[, .SD[.N], by='Date']
>
> -steve
>
> On Wed, Aug 14, 2013 at 2:01 PM, William Dunlap <wdun...@tibco.com> wrote:
>> A somewhat faster version (for datasets with lots of dates, assuming it is
>> sorted by date and time) is
>> isLastInRun <- function(x) c(x[-1] != x[-length(x)], TRUE)
>> f3 <- function(dataFrame) {
>> dataFrame[ isLastInRun(dataFrame$Date), ]
>> }
>> where your two suggestions, as functions, are
>> f1 <- function (dataFrame) {
>> dataFrame[unlist(with(dataFrame, tapply(Time, list(Date), FUN =
>> function(x) x == max(x)))), ]
>> }
>> f2 <- function (dataFrame) {
>> dataFrame[cumsum(with(dataFrame, tapply(Time, list(Date), FUN =
>> which.max))), ]
>> }
>>
>> Bill Dunlap
>> Spotfire, TIBCO Software
>> wdunlap tibco.com
>>
>>
>>> -----Original Message-----
>>> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
>>> Behalf
>>> Of arun
>>> Sent: Wednesday, August 14, 2013 1:08 PM
>>> To: Noah Silverman
>>> Cc: R help
>>> Subject: Re: [R] How to extract last value in each group
>>>
>>> Hi,
>>> Try:
>>> dat1<- read.table(text="
>>> Date Time O H L C U D
>>> 06/01/2010 1358 136.40 136.40 136.35 136.35 2 12
>>> 06/01/2010 1359 136.40 136.50 136.35 136.50 9 6
>>> 06/01/2010 1400 136.45 136.55 136.35 136.40 8 7
>>> 06/01/2010 1700 136.55 136.55 136.55 136.55 1 0
>>> 06/02/2010 331 136.55 136.70 136.50 136.70 36 6
>>> 06/02/2010 332 136.70 136.70 136.65 136.65 3 1
>>> 06/02/2010 334 136.75 136.75 136.75 136.75 1 0
>>> 06/02/2010 335 136.80 136.80 136.80 136.80 4 0
>>> 06/02/2010 336 136.80 136.80 136.80 136.80 8 0
>>> 06/02/2010 337 136.75 136.80 136.75 136.80 1 2
>>> 06/02/2010 338 136.80 136.80 136.80 136.80 3 0
>>> ",sep="",header=TRUE,stringsAsFactors=FALSE)
>>>
>>> dat1[unlist(with(dat1,tapply(Time,list(Date),FUN=function(x) x==max(x)))),]
>>> # Date Time O H L C U D
>>> #4 06/01/2010 1700 136.55 136.55 136.55 136.55 1 0
>>> #11 06/02/2010 338 136.80 136.80 136.80 136.80 3 0
>>> #or
>>> dat1[cumsum(with(dat1,tapply(Time,list(Date),FUN=which.max))),]
>>> Date Time O H L C U D
>>> 4 06/01/2010 1700 136.55 136.55 136.55 136.55 1 0
>>> 11 06/02/2010 338 136.80 136.80 136.80 136.80 3 0
>>>
>>> #or
>>> dat1[as.logical(with(dat1,ave(Time,Date,FUN=function(x) x==max(x)))),]
>>> # Date Time O H L C U D
>>> #4 06/01/2010 1700 136.55 136.55 136.55 136.55 1 0
>>> #11 06/02/2010 338 136.80 136.80 136.80 136.80 3 0
>>> A.K.
>>>
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: Noah Silverman <noahsilver...@ucla.edu>
>>> To: "R-help@r-project.org" <r-help@r-project.org>
>>> Cc:
>>> Sent: Wednesday, August 14, 2013 3:56 PM
>>> Subject: [R] How to extract last value in each group
>>>
>>> Hello,
>>>
>>> I have some stock pricing data for one minute intervals.
>>>
>>> The delivery format is a bit odd. The date column is easily parsed and
>>> used as an index
>>> for an its object. However, the time column is just an integer (1:1807)
>>>
>>> I just need to extract the *last* entry for each day. Don't actually care
>>> what time it was,
>>> as long as it was the last one.
>>>
>>> Sure, writing a big nasty loop would work, but I was hoping that someone
>>> would be able
>>> to suggest a faster way.
>>>
>>> Small snippet of data below my sig.
>>>
>>> Thanks!
>>>
>>>
>>> --
>>> Noah Silverman, M.S., C.Phil
>>> UCLA Department of Statistics
>>> 8117 Math Sciences Building
>>> Los Angeles, CA 90095
>>>
>>> --------------------------------------------------------------------------
>>>
>>> Date Time O H L C U D
>>> 06/01/2010 1358 136.40 136.40 136.35 136.35 2 12
>>> 06/01/2010 1359 136.40 136.50 136.35 136.50 9 6
>>> 06/01/2010 1400 136.45 136.55 136.35 136.40 8 7
>>> 06/01/2010 1700 136.55 136.55 136.55 136.55 1 0
>>> 06/02/2010 331 136.55 136.70 136.50 136.70 36 6
>>> 06/02/2010 332 136.70 136.70 136.65 136.65 3 1
>>> 06/02/2010 334 136.75 136.75 136.75 136.75 1 0
>>> 06/02/2010 335 136.80 136.80 136.80 136.80 4 0
>>> 06/02/2010 336 136.80 136.80 136.80 136.80 8 0
>>> 06/02/2010 337 136.75 136.80 136.75 136.80 1 2
>>> 06/02/2010 338 136.80 136.80 136.80 136.80 3 0
>>> ______________________________________________
>>> 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.
>>
>> ______________________________________________
>> 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.
>
>
>
> --
> Steve Lianoglou
> Computational Biologist
> Bioinformatics and Computational Biology
> Genentech
--
Steve Lianoglou
Computational Biologist
Bioinformatics and Computational Biology
Genentech
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and provide commented, minimal, self-contained, reproducible code.
