Return df with a columns values that occur more than once [duplicate]

Question

I have a data frame df, and I am trying to subset all rows that have a value in column B occur more than once in the dataset.

I tried using table to do it, but am having trouble subsetting from the table:

t<-table(df$B)

Then I try subsetting it using:

subset(df, table(df$B)>1)

And I get the error

"Error in x[subset & !is.na(subset)] : object of type 'closure' is not subsettable"

How can I subset my data frame using table counts?

Answer 1

Here is a dplyr solution (using mrFlick's data.frame)

library(dplyr)
newd <-  dd %>% group_by(b) %>% filter(n()>1) #
newd
#    a b 
# 1  1 1 
# 2  2 1 
# 3  5 4 
# 4  6 4 
# 5  7 4 
# 6  9 6 
# 7 10 6 

Or, using data.table

setDT(dd)[,if(.N >1) .SD,by=b]

Or using base R

dd[dd$b %in% unique(dd$b[duplicated(dd$b)]),]

Answer 2

May I suggest an alternative, faster way to do this with data.table?

require(data.table) ## 1.9.2
setDT(df)[, .N, by=B][N > 1L]$B

(or) you can couple .I (another special variable - see ?data.table) which gives the corresponding row number in df, along with .N as follows:

setDT(df)[df[, .I[.N > 1L], by=B]$V1]

(or) have a look at @mnel's another for another variation (using yet another special variable .SD).