String sequence starting with a running character and then with a vector of numbers

Question

I want to have the following string sequence as result:

"2016-01" "2016-02" "2016-03" "2016-04" "2016-05" "2016-06" "2016-07" "2016-08" "2016-09" "2016-10" "2016-11" "2016-12" "2017-01" "2017-02" "2017-03" "2017-04" "2017-05" "2017-06" "2017-07" "2017-08" "2017-09" "2017-10" "2017-11" "2017-12" "2018-01" "2018-02" "2018-03" "2018-04" "2018-05" "2018-06" "2018-07" "2018-08" "2018-09" "2018-10" "2018-11" "2018-12" "2019-01" "2019-02" "2019-03" "2019-04" "2019-05" "2019-06" "2019-07" "2019-08" "2019-09" "2019-10" "2019-11" "2019-12" "2020-01" "2020-02" "2020-03" "2020-04" "2020-05" "2020-06" "2020-07" "2020-08" "2020-09" "2020-10" "2020-11" "2020-12"

and I wrote the following code:

c(sprintf("2016-%02d", 1:12), 
  sprintf("2017-%02d", 1:12),
  sprintf("2018-%02d", 1:12),
  sprintf("2019-%02d", 1:12),
  sprintf("2020-%02d", 1:12))

Is there any other shorter and eleganter solution? For example any suggestion to combine the first part of sprintf ?

Answer 1

1) This will give the indicated character vector or just use ym to get yearmon class vector which may be more convenient as it is represented internally as year + fraction where fraction is 0 for Jan, 1/12 for Feb, ..., 11/12 for Dec and so may be manipulated in relevant ways such as using it as the X axis for a plot.

library(zoo)
ym <- seq(as.yearmon("2016-01"),  as.yearmon("2020-12"), 1/12)
format(ym, "%Y-%m")

An alternate way of forming ym is:

ym <- ts(start = 2006, end = c(2012, 12), freq = 12) |> 
  time() |>
  as.yearmon()

2) This would also work using only base R. You might prefer to just use d as it could be used in plotting as well.

d <- seq(as.Date("2016-01-01"), as.Date("2020-12-01"), by = "month")
format(d, "%Y-%m")

3) This base solution is shorter but lacks the flexibility of using Date or yearmon classes.

sprintf("%d-%02d", rep(2006:2012, each = 12), 1:12)

Answer 2

With base R, try:

seq.Date(from = as.Date("2016-01-01"), to = as.Date("2020-12-01"), by = "1 month") |> format("%Y-%m")

 [1] "2016-01" "2016-02" "2016-03" "2016-04" "2016-05" "2016-06" "2016-07"
 [8] "2016-08" "2016-09" "2016-10" "2016-11" "2016-12" "2017-01" "2017-02"
[15] "2017-03" "2017-04" "2017-05" "2017-06" "2017-07" "2017-08" "2017-09"
[22] "2017-10" "2017-11" "2017-12" "2018-01" "2018-02" "2018-03" "2018-04"
[29] "2018-05" "2018-06" "2018-07" "2018-08" "2018-09" "2018-10" "2018-11"
[36] "2018-12" "2019-01" "2019-02" "2019-03" "2019-04" "2019-05" "2019-06"
[43] "2019-07" "2019-08" "2019-09" "2019-10" "2019-11" "2019-12" "2020-01"
[50] "2020-02" "2020-03" "2020-04" "2020-05" "2020-06" "2020-07" "2020-08"
[57] "2020-09" "2020-10" "2020-11" "2020-12"