Format date as Year/Quarter - r

Question

I have the following dataframe:
Data <- data.frame(
date = c("2001-01-01", "2001-02-01", "2001-03-01", "2001-04-01", "2001-05-01", "2001-06-01"),
qtr = c("NA", "NA","NA","NA","NA","NA")
)
I want to fill Data$qtr with Year/Quater - f.e. 01/01 (I need this format!).
I wrote a function:
fun <- function(x) {
if(x == "2001-01-01" | x == "2001-02-01" | x == "2001-03-01") y <- "01/01"
if(x == "2001-04-01" | x == "2001-05-01" | x == "2001-06-01") y <- "01/02"
return(y)
}
n$qtr <- sapply(n$date, fun)
But it does not work. I always get the error message:
Error in FUN(X[[1L]], ...) : Object 'y' not found
Why?

Answer 1

You need to explicilty Vectorize your function:
fun_v <- Vectorize(fun, "x")
fun_v(Data$date)
#[1] "01/01" "01/01" "01/01" "01/02" "01/02" "01/02"
However, when it comes to more or less standard tasks (such as datetime manipulations), there's always a solution already available:
library(zoo)
yq <- as.yearqtr(Data$date, format = "%Y-%m-%d")
yq
#[1] "2001 Q1" "2001 Q1" "2001 Q1" "2001 Q2" "2001 Q2" "2001 Q2"
To convert to your specific format, use
format(yq, format = "%y/0%q")
#[1] "01/01" "01/01" "01/01" "01/02" "01/02" "01/02"

Answer 2

I have been loving the lubridate package for working with dates. Super slick. The quarter function finds the quarter (of course) and then just pair that with the year.
library(lubridate)
Data <- Data %>%
mutate(qtr = paste0(substring(year(date),3,4),"/0",quarter(date)))
If you are not familiar with the %>% from magrittr the first line basically says "use data frame called Data" and the second line says "mutate (or add) a column called qtr"
EDIT 2021-Q2
If the "YY/QQ" format is not critical, then a quick and safe way to get the year and the quarter is:
library(lubridate)
Data %>%
mutate(qtr = quarter(date, with_year = T))

Answer 3

Using base functions:
Data$date <- as.Date(Data$date)
Data$qtr <- paste(format(Data$date, "%y"),
sprintf("%02i", (as.POSIXlt(Data$date)$mon) %/% 3L + 1L),
sep="/")
# date qtr
# 1 2001-01-01 01/01
# 2 2001-02-01 01/01
# 3 2001-03-01 01/01
# 4 2001-04-01 01/02
# 5 2001-05-01 01/02
# 6 2001-06-01 01/02

Answer 4

another option would be:
Data$qtr <- lubridate::quarter(Data$date, with_year = T)

Answer 5

I made a similar format using quarters() and sub() in R:
Data$qtr <- paste(format(Data$date, "%y/"), 0,
sub( "Q", "", quarters(Data$date) ), sep = "")

Answer 6

The data.table package and its IDate class have some nice convenience functions (e.g. quarter(), year()), similar to those of lubridate available. paste0() them together as you please.
Data <- data.frame(
date = c("2001-01-01", "2001-02-01", "2001-03-01",
"2001-04-01", "2001-05-01", "2001-06-01")
)
require(data.table)
setDT(Data)
Data[ , date := as.IDate(date) ] # data.table s integer based date class
Data[ , qtr := paste0(year(date), '/', quarter(date)) ]
# your specific format
Data[ , qt2 := paste0(substr(year(date),3,4), '/', '0', quarter(date)) ]

Answer 7

tidyverse's clock gives an alternative, with the advantage of not loosing the original day, with calendar_narrow and date precision:
library(clock)
library(dplyr)
#Function to convert a date to year-quarter
toQ <- . %>%
date_parse() %>%
as_year_quarter_day() %>%
calendar_narrow("quarter")
Data %>%
mutate(qtr = toQ(date))
output
date qtr
1 2001-01-01 2001-Q1
2 2001-02-01 2001-Q1
3 2001-03-01 2001-Q1
4 2001-04-01 2001-Q2
5 2001-05-01 2001-Q2
6 2001-06-01 2001-Q2

Answer 8

Another (longer) way
of doing it using if statements is this:
month <- as.numeric(format(date, format = "%m"))[1]
if (month < 4) {
quarter <- paste( format(date, format = "%Y")[1], "Q1", sep="-")
} else if (month > 3 & month < 7) {
quarter <- paste( format(date, format = "%Y")[1], "Q2", sep="-")
} else if (month > 6 & month < 10) {
quarter <- paste( format(date, format = "%Y")[1], "Q3", sep="-")
} else if (month > 9) {
quarter <- paste( format(date, format = "%Y")[1], "Q4", sep="-")
}
Returns a string in the format:
> quarter
[1] "2001-Q1"
Then you could extend that using a loop.

Answer 9

yq=function(x,prefix="%Y",combine="Q") paste0(ifelse(is.null(prefix),"",format(x,"%Y")),floor(as.numeric(format(x,"%m"))/3-1e-3)+1,sep=combine)
this gives the flexibility of returning any format back that has the quarter in it
no need for chron or zoo
as for your example
yq(as.Date("2013-04-30"),prefix="%y",combine="/0")
> [1] "13/02"

Answer 10

In case someone is looking for a format such as 1Q21 for 1st quarter 21, I used #Roland answer above and made a small change towards:
paste(sprintf("%2i", (as.POSIXlt(Notional$Date)$mon) %/% 3L + 1L), format(Notional$Date, "%y"),sep="Q")