grates (version 1.4.3)

yearmonth_class: Yearmonth class

Description

<grates_yearmonth> objects represent, unsurprisingly, years and associated months. Internally they are stored as the number of months (starting at 0) since the Unix Epoch (1970-01-01). Precision is only to the month level (i.e. the day of the month is always dropped).

Usage

yearmonth(year = integer(), month = integer())
as_yearmonth(x, ...)
# S3 method for default
as_yearmonth(x, ...)
# S3 method for Date
as_yearmonth(x, ...)
# S3 method for POSIXt
as_yearmonth(x, ...)
# S3 method for character
as_yearmonth(x, ...)
# S3 method for factor
as_yearmonth(x, ...)
new_yearmonth(x = integer())
is_yearmonth(xx)

Value

A <grates_yearmonth> object.

Arguments

year

[integer]

Vector representing the year associated with month.

double vectors will be converted via as.integer(floor(x)).

month

[integer]

Vector representing the month associated with year.

double vectors will be converted via as.integer(floor(x)).

x, xx

R objects.

...

Only used for character input where additional arguments are passed through to as.Date().

Details

yearmonth() is a constructor for <grates_yearmonth> objects. It takes a vector of year and a vector of month values as inputs. Length 1 inputs will be recycled to the length of the other input and double vectors will be converted to integer via as.integer(floor(x)).

as_yearmonth() is a generic for coercing input in to <grates_yearmonth>.

• Character input is first parsed using as.Date().

• POSIXct and POSIXlt are converted with their timezone respected.

new_yearmonth() is a minimal constructor for <grates_yearmonth> objects aimed at developers. It takes, as input, the number of months (starting at 0) since the Unix Epoch, that you wish to represent. double vectors will again be converted to integer via as.integer(floor(x)).

References

The algorithm to convert between dates and months relative to the UNIX Epoch comes from the work of Davis Vaughan in the unreleased datea package

See Also

new_month() and as_month() and for grouping of consecutive months.

Examples

# date coercion
as_yearmonth(Sys.Date())

# POSIXt coercion
as_yearmonth(as.POSIXct("2019-03-04 01:01:01", tz = "America/New_York"))

# character coercion
as_yearmonth("2019-05-03")

# construction
yearmonth(year = 2000, month = 3)

# direct construction
d <- seq.Date(from = as.Date("1970-01-01"), by = "month", length.out = 10)
stopifnot(
    identical(
        as_yearmonth(d),
        new_yearmonth(0:9)
    )
)