mondate (version 0.9.10.01)

mondate-methods: Create an instance of the mondate class

Description

All purpose mondate constructor / coercer.

Usage

mondate(x, 
        displayFormat = getOption("mondate.displayFormat", default = .default.displayFormat), 
        timeunits = getOption("mondate.timeunits", default = .default.timeunits),
        ...)
    ## S3 method for class 'mondate':
mondate(x, displayFormat, timeunits, ...)
    ## S3 method for class 'numeric':
mondate(x, displayFormat, timeunits, ...)
    ## S3 method for class 'Date':
mondate(x, displayFormat, timeunits, ...)
    ## S3 method for class 'POSIXt':
mondate(x, displayFormat, timeunits, ...)
    ## S3 method for class 'character':
mondate(x, displayFormat, timeunits, format = "", ...)
    ## S3 method for class 'array':
mondate(x, displayFormat, timeunits, ...)
    ## S3 method for class 'missing':
mondate(x, displayFormat, timeunits, ...)
    ## S3 method for class 'ANY':
mondate(x, displayFormat, timeunits, ...)

Arguments

x

an Robject to convert to a mondate. Can be another mondate, a character representing a date, a date, a numeric, or an object which converts to a numeric with as.numeric(x). More details below.

displayFormat

character string representing the date format with which to display the mondate. The default.displayFormat is determined according to Sys.getlocale("LC_TIME"): if it contains the words "United States", the default

timeunits

character string "months" (default), "years", or "days" indicating the units in which date arithmetic will be carried out.

format

format string for converting a character to a Date (using as.Date, x, format, ...) from which the mondate value is determined.

...

arguments to be passed to other methods.

See Also

POSIXt, yearmon, yearqtr

Examples

mondate("1-31-2010") # Jan. 31, 2010
mondate(60)          # 60 months after 12/31/1999, so Dec. 31, 2004
dat <- as.Date("2010-1-31")
(M <- mondate(dat))    # Jan. 31, 2010
x <- 12 * 1:6
mondate(x)           # first 6 yearends in 2000's
y <- x + 12
mondate(cbind(x,y))  # bounding dates of first 6 years of millennium
(y <- mondate(1:6,timeunits="years")) # first 6 yearends, 'years' timeunits 
# The results of date arithmetic on y will be displayed in "years".
# E.g., the differences of y can be calculated as:
tail(y,-1) - head(y,-1)# vector of five 1's, with "timeunits" attribute = "years"
as.numeric(x)
as.numeric(y)        # the underlying numeric representations are the same

# Demonstrating "infinite" dates
y <- c(y,Inf)
y                    # last element shows as Inf
tail(y,-1) - head(y,-1)# last element is now infinity

# The zoo examples point out a difference between zoo and mondate.
#   zoo assumes that the zero-th part of a month or quarter is the first
#   day of the month or quarter, whereas mondate assumes that it is 
#   the instant before the first day of the month or quarter.
# Since frac=0 is zoo's as.Date coersion default, a month or quarter in 
#   zoo's sense converts to the end of the first day rather than
#   the beginning.
library(zoo)
x <- ts(1:10, frequency = 4, start = c(1959, 2)) # starting 2nd qtr of 1959
x
# There is no method for class 'ts' so x is coerced (successfully) 
#   because that class has an as.Date method, but with a warning.
# The result is a vector of length 10 representing the close of business
#   at the end of the first day of each of the given quarters.
mondate(x)      

# The yearmon class will identify any day in June 2010 with that month.
as.yearmon("2010-6-15") 
mondate(as.yearmon("2010-6-15"))         # end of first day of June 2010
mondate(as.yearmon("2010-6-15"), frac=1) # end of  last day of June 2010
mondate(as.yearqtr("2010-2"), frac=1)    # same

# The if missing, displayFormat will be determined from the character input
x <- mondate("2010-12-31")
x               # x displays in the input European format
# The provided, displayFormat must match the format of the character input
#   or NA's will result.
mondate("2010-12-31", displayFormat = "%m-%d-%Y") # results in NA

# Always display x using just the year
x <- mondate(as.Date("2012-3-1"), displayFormat="%Y")
x                # shows as the year 2012, but month and day are nevertheless retained
month(x)         # 3
day(x)           # 1