Consider the sample data
df <-
structure(
list(
id = c(1L, 1L, 1L, 1L, 2L, 2L, 3L),
A = c(20L, 12L, 13L, 8L, 11L, 21L, 17L),
B = c(1L, 1L, 0L, 0L, 1L, 0L, 0L)
),
.Names = c("id", "A", "B"),
class = "data.frame",
row.names = c(NA,-7L)
)
Each id (stored in column 1) has varying number of entries for column A
and B
. In the example data, there are four observations with id = 1
. I am looking for a way to subset this data in R so that there will be at most 3 entries for for each id and finally create another column (labelled as C) which consists of the order of each id. The expected output would look like:
df <-
structure(
list(
id = c(1L, 1L, 1L, 2L, 2L, 3L),
A = c(20L, 12L, 13L, 11L, 21L, 17L),
B = c(1L, 1L, 0L, 1L, 0L, 0L),
C = c(1L, 2L, 3L, 1L, 2L, 1L)
),
.Names = c("id", "A", "B","C"),
class = "data.frame",
row.names = c(NA,-6L)
)
Your help is much appreciated.