[R] problem of data manipulation

[William Dunlap]

> -----Original Message-----
> From: Bert Gunter [mailto:gunter.berton at gene.com] 
> Sent: Monday, January 18, 2010 12:32 PM
> To: William Dunlap; 'rusers.sh'; r-help at r-project.org
> Subject: RE: [R] problem of data manipulation
> 
> Absolutely... so long as you assume the dates are in order -- 
> or at least
> that the earliest date of a group appears first. 
> 
> -- Bert
> 

Yes, I forgot to mention that requirement.  When
there are a lot of small groups run-based methods
(sort then deal with a run at a time) can save a
lot of time.  They may also make the intent of
the code more clear, but not everyone sees it that way.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 
   
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On
> Behalf Of William Dunlap
> Sent: Monday, January 18, 2010 12:15 PM
> To: Bert Gunter; rusers.sh; r-help at r-project.org
> Subject: Re: [R] problem of data manipulation
> 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org 
> > [mailto:r-help-bounces at r-project.org] On Behalf Of Bert Gunter
> > Sent: Monday, January 18, 2010 11:54 AM
> > To: 'rusers.sh'; r-help at r-project.org
> > Subject: Re: [R] problem of data manipulation
> > 
> > One way to do it:
> > 
> > 1. Convert your date column to the Date class using the 
> > as.Date() function.
> > This allows you to do the necessary arithmetic on the dates below.
> > dt <- as.Date(a[,4],"%d/%m/%Y")
> > 
> > 2. Create a factor out of your first three columns whose 
> > levels are in the
> > same order as the unique rows. Something likes the following 
> > should do it:
> > fac <- do.call(paste,a[,-4])
> > fac <- factor(fac, levels=unique(fac))
> > 
> > This allows you to choose the groups of rows whose dates you 
> > wish to compare
> > and maintain their correct order in the data frame
> > 
> > 3. Then use tapply: 
> > a[unlist(tapply(dt,fac,function(x)x-min(x) < 7)),]
> 
> You can do this without unpacking and repacking
> the data.frame (with tapply) based on the following
> sort of calculation:
> 
>   > isFirstInRun <- function(x)c(TRUE, x[-1] != x[-length(x)])
>   > f <- with(a, isFirstInRun(var1) | isFirstInRun(var2) |
> isFirstInRun(var3))
>   > firstRowInRun <- which(f)
>   > runNumber <- cumsum(f)
>   > dt <- as.Date(a$var4, "%d/%m/%Y")
>   > DaysSinceStartOfRun <- dt - dt[firstRowInRun[runNumber]]
>   > DaysSinceStartOfRun
>   Time differences in days
>   [1]  0  0  3  0  4 12
>   > a[ DaysSinceStartOfRun < 7, ]
>     var1 var2 var3       var4
>   1    s    1    2 01/01/1999
>   2    c    1    2 10/02/2000
>   3    c    1    2 13/02/2000
>   4    n    2    1 11/02/2000
>   5    n    2    1 15/02/2000
> 
> Is that what you wanted?
> 
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com 
> > 
> > (unlist is needed to remove the list structure and 
> > concatenate the logical
> > indices to obtain the subscripting vector).
> > 
> > Bert Gunter
> > Genentech Nonclinical Statistics
> > 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org 
> > [mailto:r-help-bounces at r-project.org] On
> > Behalf Of rusers.sh
> > Sent: Monday, January 18, 2010 10:40 AM
> > To: r-help at r-project.org
> > Subject: [R] problem of data manipulation
> > 
> > Hello,
> >   See my problem below.
> > a<-data.frame(c("s","c","c","n","n","n"),c(rep(1,3),rep(2,3)),
> > c(rep(2,3),rep
> > (1,3)),c("01/01/1999","10/02/2000","13/02/2000","11/02/2000","
> > 15/02/2000","2
> > 3/02/2000"))
> > colnames(a)<-c("var1","var2","var3","var4")
> > > a
> >   var1 var2 var3       var4
> > 1    s    1    2    01/01/1999
> > 2    c    1    2    10/02/2000
> > 3    c    1    2    13/02/2000
> > 4    n    2    1    11/02/2000
> > 5    n    2    1    15/02/2000
> > 6    n    2    1    23/02/2000
> > 
> >   I want to select the observations whose difference of 
> > "var4" is less than
> > 7 for the cases with the same values of var1,var2 andvar3.
> >   The obervations have the same var1, var2 and var3 are, 
> > part1 (obs2 and
> > obs3) and part2 (obs4,obs5, and obs6).
> >   For obs2 and obs3, their date difference is less than 7, so 
> > we donot need
> > to delete any of them.
> >   For obs4,obs5, and obs6,we can see that obs6 should be 
> > deleted becuase its
> > date is over 7 dyas longer than obs4.
> >   So the final dataset should obs1,obs2,obs3,obs4, and obs5.
> >   I have a lot of observations in my dataset, so i hope to do this
> > automatically.  Any ideas on this?
> >   Thanks.
> > -- 
> > -----------------
> > Jane Chang
> > Queen's
> > 
> > 	[[alternative HTML version deleted]]
> > 
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> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide 
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> > and provide commented, minimal, self-contained, reproducible code.
> > 
> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
>