[R] Counting duplicates in a dataframe

[PIKAL Petr]

Hi

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of asafwe
> Sent: Monday, October 22, 2012 4:02 AM
> To: r-help at r-project.org
> 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.

How is it realated with duplicates?

Do you want something like that?
xtabs(~Gender+Dosage, data=some.data.frame)

Regards
Petr

> 
> 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
> 
> 
> 
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