Create year-quarter variables from dates

lubridate_quarters.R

library(dplyr)
library(lubridate)
library(stringr)

# let's say my data has some dates in it  -- these are just random dates for an example 
# and I want to code them to year and quarter

df <- data.frame(
  # random dates between 2020-01-01 and 2022-02-14
  date = lubridate::ymd('2020-01-01') + sample.int(775, 100, replace = TRUE))

df <- df %>% 
  mutate(

    # extract the year
    year = lubridate::year(date), 

    # create year breaks for each row
    year_start = lubridate::ymd(stringr::str_c(year, "-01-01")),
    year_q1_end = year_start + round(365/4),
    year_q2_end = year_start + round(365/4*2),
    year_q3_end = year_start + round(365/4*3),
    year_q4_end = lubridate::ymd(stringr::str_c(year, "-12-31")),

      # code the quarter
    quarter = case_when(
      date >= year_start & date <= year_q1_end ~ "Q1",
      date > year_q1_end & date <= year_q2_end ~ "Q2",
      date > year_q2_end & date <= year_q3_end ~ "Q3",
      date > year_q3_end & date <= year_q4_end ~ "Q4"),

    # create year_quarter character variable
    year_quarter = stringr::str_c(year, "-", quarter),

    # code year_quarter to ordered factor variable
    year_quarter = factor(year_quarter, 
      levels = stringr::str_c(rep(2020:2022, each=4), "-", 
        stringr::str_c("Q", 1:4)))
    )

# print
df %>% arrange(df) %>% 
  select(date, year_quarter)

##           date year_quarter
## 1   2020-01-11      2020-Q1
## 2   2020-01-11      2020-Q1
## 3   2020-01-24      2020-Q1
## 4   2020-02-02      2020-Q1
## 5   2020-02-04      2020-Q1
## 6   2020-02-06      2020-Q1
## 7   2020-02-07      2020-Q1
## 8   2020-02-10      2020-Q1
## 9   2020-02-12      2020-Q1
## 10  2020-02-15      2020-Q1
## 11  2020-02-19      2020-Q1
## 12  2020-03-14      2020-Q1
## 13  2020-03-27      2020-Q1
## 14  2020-04-19      2020-Q2
## 15  2020-04-26      2020-Q2
## 16  2020-05-18      2020-Q2
## 17  2020-05-20      2020-Q2
## 18  2020-05-20      2020-Q2
## 19  2020-06-02      2020-Q2
## 20  2020-06-22      2020-Q2
## 21  2020-06-23      2020-Q2
## 22  2020-06-28      2020-Q2
## 23  2020-07-14      2020-Q3
## 24  2020-07-22      2020-Q3
## 25  2020-07-26      2020-Q3
## 26  2020-08-08      2020-Q3
## 27  2020-09-23      2020-Q3
## 28  2020-09-29      2020-Q3
## 29  2020-09-30      2020-Q3
## 30  2020-10-02      2020-Q4
## 31  2020-10-03      2020-Q4
## 32  2020-10-07      2020-Q4
## 33  2020-10-11      2020-Q4
## 34  2020-10-11      2020-Q4
## 35  2020-10-25      2020-Q4
## 36  2020-10-25      2020-Q4
## 37  2020-10-27      2020-Q4
## 38  2020-10-29      2020-Q4
## 39  2020-10-30      2020-Q4
## 40  2020-10-30      2020-Q4
## 41  2020-10-31      2020-Q4
## 42  2020-11-01      2020-Q4
## 43  2020-11-18      2020-Q4
## 44  2020-11-24      2020-Q4
## 45  2020-11-24      2020-Q4
## 46  2020-12-06      2020-Q4
## 47  2021-01-05      2021-Q1
## 48  2021-02-08      2021-Q1
## 49  2021-02-10      2021-Q1
## 50  2021-02-15      2021-Q1
## 51  2021-02-21      2021-Q1
## 52  2021-02-26      2021-Q1
## 53  2021-02-26      2021-Q1
## 54  2021-02-26      2021-Q1
## 55  2021-03-04      2021-Q1
## 56  2021-03-10      2021-Q1
## 57  2021-03-25      2021-Q1
## 58  2021-03-28      2021-Q1
## 59  2021-03-30      2021-Q1
## 60  2021-04-07      2021-Q2
## 61  2021-04-26      2021-Q2
## 62  2021-04-30      2021-Q2
## 63  2021-05-09      2021-Q2
## 64  2021-05-14      2021-Q2
## 65  2021-05-16      2021-Q2
## 66  2021-05-27      2021-Q2
## 67  2021-06-06      2021-Q2
## 68  2021-06-10      2021-Q2
## 69  2021-06-17      2021-Q2
## 70  2021-06-25      2021-Q2
## 71  2021-06-28      2021-Q2
## 72  2021-07-02      2021-Q2
## 73  2021-07-05      2021-Q3
## 74  2021-07-05      2021-Q3
## 75  2021-07-16      2021-Q3
## 76  2021-07-17      2021-Q3
## 77  2021-07-18      2021-Q3
## 78  2021-07-30      2021-Q3
## 79  2021-08-02      2021-Q3
## 80  2021-08-17      2021-Q3
## 81  2021-08-25      2021-Q3
## 82  2021-08-29      2021-Q3
## 83  2021-08-31      2021-Q3
## 84  2021-08-31      2021-Q3
## 85  2021-09-14      2021-Q3
## 86  2021-09-15      2021-Q3
## 87  2021-09-20      2021-Q3
## 88  2021-09-25      2021-Q3
## 89  2021-09-27      2021-Q3
## 90  2021-10-21      2021-Q4
## 91  2021-10-22      2021-Q4
## 92  2021-10-30      2021-Q4
## 93  2021-11-05      2021-Q4
## 94  2021-11-24      2021-Q4
## 95  2021-11-26      2021-Q4
## 96  2021-11-30      2021-Q4
## 97  2022-01-02      2022-Q1
## 98  2022-01-09      2022-Q1
## 99  2022-01-13      2022-Q1
## 100 2022-02-01      2022-Q1