mathijsdevaan  wrote on 12/09/2010 04:21:54 PM:
> I have two columns with data (both identifiers - it's an affiliation 
list)
> and I would like to delete the rows in which the observations in the 
second
> column have a frequency < 5 in the entire second column. Example:
> 
> 1     a
> 1     b
> 1     c
> 2     a
> 2     b
> 2     d
> 
> Let's say, I would like to delete the rows in which the observation in 
the
> second column has a frequency < 2 in the entire second column. This 
would
> result in:
> 
> 1     a
> 1     b
> 2     a
> 2     b
> 
> How can I do this? Thanks in advance!
> 

It's not clear whether you want to delete rows where the value second 
column occurs less than 5 times or appears less than 2 times.  I'll assume 
the latter.

foo <- data.frame(k=rep(1:2, each=3), x=letters[c(1,2,3,1,2,4)])
bar <- subset(foo, x %in% names(table(foo$x))[table(foo$x)>=2])

No doubt others can write this more succinctly.

-- 
Curt Seeliger, Data Ranger
Raytheon Information Services - Contractor to ORD
seeliger.curt@epa.gov
541/754-4638

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