say I have a df like so:
number date
123 2022-01-01
567 2022-01-01
123 2022-01-04
763 2022-01-05
567 2022-01-06
123 2022-01-09
I want to count the occurrence of each number by expanding the range row-by-row. so my expected output would be
number date occurrence
123 2022-01-01 1
567 2022-01-01 1
123 2022-01-04 2
763 2022-01-05 1
567 2022-01-06 2
123 2022-01-09 3
>Solution :
base R
dat$occurrence <- ave(dat$number, dat$number, FUN = seq_along)
dat
# number date occurrence
# 1 123 2022-01-01 1
# 2 567 2022-01-01 1
# 3 123 2022-01-04 2
# 4 763 2022-01-05 1
# 5 567 2022-01-06 2
# 6 123 2022-01-09 3
data.table
library(data.table)
as.data.table(dat)[, occurrence := seq_len(.N), by = number ][]
# number date occurrence
# <int> <char> <int>
# 1: 123 2022-01-01 1
# 2: 567 2022-01-01 1
# 3: 123 2022-01-04 2
# 4: 763 2022-01-05 1
# 5: 567 2022-01-06 2
# 6: 123 2022-01-09 3
Data
dat <- structure(list(number = c(123L, 567L, 123L, 763L, 567L, 123L), date = c("2022-01-01", "2022-01-01", "2022-01-04", "2022-01-05", "2022-01-06", "2022-01-09")), row.names = c(NA, -6L), class = "data.frame")