And another way:
library(plyr)
ddply(dta,"A",summarise,B=length(B))

Felipe D. Carrillo
Supervisory Fishery Biologist
Department of the Interior
US Fish & Wildlife Service
California, USA
http://www.fws.gov/redbluff/rbdd_jsmp.aspx


From: David L Carlson <dcarlson@tamu.edu>
>To: 'Mat' <matthias.weber@fnt.de>; r-help@r-project.org 
>Sent: Monday, December 10, 2012 7:43 AM
>Subject: Re: [R] Count cell Count by her frequency
>
>You request is not completely clear. I am assuming you want to count the
>number of different characters in B for each category in A:
>
>> A <- c("10-1", "10-1", "10-1", "10-2", "10-3")
>> B <- c("aaa", "bbb", "abc", "vvv", "ggg")
>> dta <- data.frame(A, B)
>> dta
>    A  B
>1 10-1 aaa
>2 10-1 bbb
>3 10-1 abc
>4 10-2 vvv
>5 10-3 ggg
>> a1 <- tapply(dta$B, dta$A, paste0, collapse="")
>> a2 <- strsplit(a1, "")
>> a3 <- lapply(a2, unique)
>> a4 <- sapply(a3, length)
>> dtanew <- data.frame(A=names(a4), B=a4, row.names=1:length(a4))
>> dtanew
>    A B
>1 10-1 3
>2 10-2 1
>3 10-3 1
>
>----------------------------------------------
>David L Carlson
>Associate Professor of Anthropology
>Texas A&M University
>College Station, TX 77843-4352
>
>> -----Original Message-----
>> From: r-help-bounces@r-project.org [mailto:r-help-bounces@r-
>> project.org] On Behalf Of Mat
>> Sent: Monday, December 10, 2012 2:50 AM
>> To: r-help@r-project.org
>> Subject: [R] Count cell Count by her frequency
>> 
>> Hello togehter, i have a data.frame, with value like this:
>> 
>>        A      B
>> 1    10-1  aaa
>> 2    10-1  bbb
>> 3    10-1  abc
>> 4    10-2  vvv
>> 5    10-3  ggg
>> 
>> I want now a evaluation, which character is how often in my data.frame.
>> Like
>> this one:
>>      A        B
>> 1  10-1  3
>> 2  10-2  1
>> 3  10-3  1
>> 
>> How can i do this?
>> 
>> Thank you.
>> 
>> Mat
>> 
>> 
>> 
>> --
>> View this message in context: http://r.789695.n4.nabble.com/Count-cell-
>> Count-by-her-frequency-tp4652650.html
>> Sent from the R help mailing list archive at Nabble.com.
>> 
>> ______________________________________________
>> 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.
>
>
>
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