[R] Counting duplicates in a dataframe

[David Winsemius]

On Oct 22, 2012, at 7:48 AM, arun wrote:

> HI,
> Another way:
> dat1<-read.table(text="
> Observation Gender Dosage Alertness
> 1            1      m      a        8
> 2            2      m      a        12
> 3            3      m      a        13
> 4            4      m      a        12
> 5            5      m      b        6
> 6            6      m      b        7
> 7            7      m      b        23
> 8            8      m      b        14
> 9            9      f      a        15
> 10          10      f      a        12
> 11          11      f      a        22
> 12          12      f      a        14
> 13          13      f      b        15
> 14          14      f      b        12
> 15          15      f      b        18
> 16          16      f      b        22
> ",sep="",header=TRUE,stringsAsFactors=FALSE)
> 
> 
> tapply(dat1$Observation,list(dat1$Gender,dat1$Dosage),length)
> #  a b
> #f 4 4
> #m 4 4

How is that different than:

table(dat1$Gender, dat1$Dosage)

-- 
David.

> A.K.
> 
> ----- Original Message -----
> From: asafwe <asafw at wharton.upenn.edu>
> To: r-help at r-project.org
> Cc: 
> Sent: Sunday, October 21, 2012 10:02 PM
> Subject: [R] Counting duplicates in a dataframe
> 
> Hello,
> 
> I am looking at a two-way ANOVA dataset, and would like to count the rows in
> the dataframe with the same level of the first factor ("Gender") and the
> second factor ("Dosage"). In other words, I am interested in the number of
> observations per each "cell" in a (not necessarily balanced) two-way layout.
> 
> What is the simplest way to do this?
> 
> Thanks a lot,
> 
> Asaf
> 
>    Observation Gender Dosage Alertness
> 1            1      m      a         8
> 2            2      m      a        12
> 3            3      m      a        13
> 4            4      m      a        12
> 5            5      m      b         6
> 6            6      m      b         7
> 7            7      m      b        23
> 8            8      m      b        14
> 9            9      f      a        15
> 10          10      f      a        12
> 11          11      f      a        22
> 12          12      f      a        14
> 13          13      f      b        15
> 14          14      f      b        12
> 15          15      f      b        18
> 16          16      f      b        22
> 
> 
> 
> --
> View this message in context: http://r.789695.n4.nabble.com/Counting-duplicates-in-a-dataframe-tp4646954.html
> Sent from the R help mailing list archive at Nabble.com.
> 
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> 
> ______________________________________________
> 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.

David Winsemius, MD
Alameda, CA, USA