anyone knows how to get the counts of every element of a column in it self [duplicate]

Answer 1

Using ddply

library(plyr)
ddply(mydata, .(v), mutate, counts = length(v))

#  v counts
#1 1      2
#2 1      2
#3 2      3
#4 2      3
#5 2      3
#6 3      1

Or lapply

do.call(rbind, lapply(split(mydata, mydata$v), 
        function(x){ x$counts = length(x$v); x}))

#    v counts
#1.1 1      2
#1.2 1      2
#2.3 2      3
#2.4 2      3
#2.5 2      3
#3   3      1

Answer 2

Using base R:

mydata$counts <- with(mydata, table(v)[as.character(v)])

Answer 3

> mydata
  v
1 1
2 1
3 2
4 2
5 2
6 3

I would use something like this:

as.data.frame(table(a))

a Freq 1 1 2 2 2 3 3 3 1

Answer 4

Another base R option with ave:

within(mydata, counts <- ave(v, v, FUN=length))

Answer 5

library(dplyr)
mutate(group_by(mydata,v),count=(length(v)))