Represent year-month

Create or coerce using yearmonth().

yearmonth(x, ...)

make_yearmonth(year = 1970L, month = 1L)

# S3 method for character
yearmonth(x, format = NULL, ...)

is_yearmonth(x)

Arguments

x

Other object.

...

Further arguments to methods.

year, month

A vector of numerics give years and months.

format

A vector of strings to specify additional formats of x (e.g. %Y%m), if a warning or an error occurs.

Value

year-month (yearmonth) objects.

Display

Use format() to display yearweek, yearmonth, and yearquarter objects in required formats. Please see strptime() details for supported conversion specifications.

See also

scale_x_yearmonth and others for ggplot2 scales

Other index functions: yearquarter(), yearweek()

Examples

# coerce POSIXct/Dates to yearmonth
x <- seq(as.Date("2016-01-01"), as.Date("2016-12-31"), by = "1 month")
yearmonth(x)
#> <yearmonth[12]>
#>  [1] "2016 Jan" "2016 Feb" "2016 Mar" "2016 Apr" "2016 May" "2016 Jun"
#>  [7] "2016 Jul" "2016 Aug" "2016 Sep" "2016 Oct" "2016 Nov" "2016 Dec"

# parse characters
yearmonth(c("2018 Jan", "2018-01", "2018 January"))
#> <yearmonth[3]>
#> [1] "2018 Jan" "2018 Jan" "2018 Jan"

# seq() and arithmetic
mth <- yearmonth("2017-11")
seq(mth, length.out = 10, by = 1) # by 1 month
#> <yearmonth[10]>
#>  [1] "2017 Nov" "2017 Dec" "2018 Jan" "2018 Feb" "2018 Mar" "2018 Apr"
#>  [7] "2018 May" "2018 Jun" "2018 Jul" "2018 Aug"
mth + 0:9
#> <yearmonth[10]>
#>  [1] "2017 Nov" "2017 Dec" "2018 Jan" "2018 Feb" "2018 Mar" "2018 Apr"
#>  [7] "2018 May" "2018 Jun" "2018 Jul" "2018 Aug"

# display formats
format(mth, format = "%y %m")
#> [1] "17 11"

# units since 1970 Jan
as.double(yearmonth("1969 Jan") + 0:24)
#>  [1] -12 -11 -10  -9  -8  -7  -6  -5  -4  -3  -2  -1   0   1   2   3   4   5   6
#> [20]   7   8   9  10  11  12

make_yearmonth(year = 2021, month = 10:11)
#> <yearmonth[2]>
#> [1] "2021 Oct" "2021 Nov"
make_yearmonth(year = 2020:2021, month = 10:11)
#> <yearmonth[2]>
#> [1] "2020 Oct" "2021 Nov"