zoo (version 1.1-1)

yearmon: An Index Class for Monthly Data

Description

"yearmon" is a class for representing monthly data.

Usage

yearmon(x)

Arguments

x

numeric (interpreted as being in years).

Value

• Returns its argument converted to class yearmon.

Details

The yearmon class is used to represent monthly data. Internally it holds the data as year plus 0 for January, 1/12 for February, 2/12 for March and so on in order that its internal representation is the same as ts class with frequency = 12. If x is not in this format it is rounded via floor(12*x + .0001)/12. There are coercion methods available for various classes including: default coercion to "yearmon" (which coerces to "numeric" first) and coercion from "yearmon" to "Date" (see below), "POSIXct", "POSIXlt", "numeric", "character".

See Also

yearqtr, zoo, zooreg, ts

Examples

x <- yearmon(2000 + seq(0, 23)/12)
x

# returned Date is the fraction of the way through
# the period given by frac (= 0 by default)
as.Date(x)
as.Date(x, frac = 1)
as.POSIXct(x)

z <- zoo(rnorm(24), x, frequency = 12)
z
as.ts(z)