month_class: Month class

In grates: Grouped Date Classes

Month class

Description

Month objects are groupings of 'n consecutive months' stored relative to the Unix Epoch. More precisely, grates_month objects are stored as the integer number (starting at 0), of n-month groups since the Unix Epoch (1970-01-01).

Usage

as_month(x, n, ...)

## Default S3 method:
as_month(x, n, ...)

## S3 method for class 'Date'
as_month(x, n, ...)

## S3 method for class 'POSIXt'
as_month(x, n, ...)

## S3 method for class 'character'
as_month(x, n, ...)

## S3 method for class 'factor'
as_month(x, n, ...)

new_month(x = integer(), n)

is_month(xx)

Arguments

x, xx	R objects.
n	⁠[integer]⁠ Number of months that are being grouped. Must be greater than 1 (use as_yearmonth() for this case).
...	Only used For character input where additional arguments are passed through to as.Date().

Details

as_month() is a generic for conversion to ⁠<grates_month>⁠.

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

• POSIXt inputs are converted with the timezone respected.

• Precision is only to the month level (i.e. the day of the month is always dropped).

new_month() is a minimal constructor for ⁠<grates_month>⁠ objects aimed at developers. It takes, as input x, the number of n-months since the Unix Epoch (1970-01-01) and the related value of n. double vectors will be converted via as.integer(floor(x)).

Value

A ⁠<grates_month>⁠ object.

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

The yearmonth class.

Examples

# date coercion
as_month(Sys.Date(), n = 2)

# character coercion
as_month("2019-05-03", n = 4)

# POSIXt coercion
as_month(as.POSIXct("2019-03-04 01:01:01", tz = "America/New_York"), n = 2)

# direct construction
d <- seq.Date(from = as.Date("1970-03-01"), by = "2 month", length.out = 10)
stopifnot(
    identical(
        as_month(d, n = 2),
        new_month(1:10, 2)
    )
)

grates documentation built on April 3, 2025, 10:49 p.m.