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Last data update: 2014.03.03

R: Functions to convert character, factor and various date...

cal.yr

R Documentation

Functions to convert character, factor and various date objects into a number, and vice versa.

Description

Dates are converted to a numerical value, giving the calendar year as a fractional number. 1 January 1970 is converted to 1970.0, and other dates are converted by assuming that years are all 365.25 days long, so inaccuracies may arise, for example, 1 Jan 2000 is converted to 1999.999. Differences between converted values will be 1/365.25 of the difference between corresponding Date objects.

Usage

  cal.yr( x, format="%Y-%m-%d", wh=NULL )
  ## S3 method for class 'cal.yr'
as.Date( x, ... )

Arguments

`x`	A factor or character vector, representing a date in format `format`, or an object of class `Date`, `POSIXlt`, `POSIXct`, `date`, `dates` or `chron` (the latter two requires the `chron` package). If `x` is a data frame, all variables in the data-frame which are of one the classes mentioned are converted to class `cal.yr`. See arguemt `wh`, though.
`format`	Format of the date values if `x` is factor or character. If this argument is supplied and `x` is a datafame, all character variables are converted to class `cal.yr`. Factors in the dataframe will be ignored.
`wh`	Indices of the variables to convert if `x` is a data frame. Can be either a numerical or character vector.
`...`	Arguments passed on from other methods.

Value

cal.yr returns a numerical vector of the same length as x, of class c("cal.yr","numeric"). If x is a data frame a dataframe with some of the columns converted to class "cal.yr" is returned.

as.Date.cal.yr returns a Date object.

Author(s)

Bendix Carstensen, Steno Diabetes Center & Dept. of Biostatistics, University of Copenhagen, bxc@steno.dk, http://BendixCarstensen.com

Examples

 # Character vector of dates:
 birth <- c("14/07/1852","01/04/1954","10/06/1987","16/05/1990",
            "12/11/1980","01/01/1997","01/01/1998","01/01/1999")
 # Proper conversion to class "Date":
 birth.dat <- as.Date( birth, format="%d/%m/%Y" )
 # Converson of character to class "cal.yr"
 bt.yr <- cal.yr( birth, format="%d/%m/%Y" )
 # Back to class "Date":
 bt.dat <- as.Date( bt.yr )
 # Numerical calculation of days since 1.1.1970:
 days <- Days <- (bt.yr-1970)*365.25
 # Blunt assignment of class:
 class( Days ) <- "Date"
 # Then data.frame() to get readable output of results:
 data.frame( birth, birth.dat, bt.yr, bt.dat, days, Days, round(Days) )

Results


R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

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Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(Epi)

Attaching package: 'Epi'

The following object is masked from 'package:base':

    merge.data.frame

> png(filename="/home/ddbj/snapshot/RGM3/R_CC/result/Epi/cal.yr.Rd_%03d_medium.png", width=480, height=480)
> ### Name: cal.yr
> ### Title: Functions to convert character, factor and various date objects
> ###   into a number, and vice versa.
> ### Aliases: cal.yr as.Date.cal.yr
> ### Keywords: manip chron
> 
> ### ** Examples
> 
>  # Character vector of dates:
>  birth <- c("14/07/1852","01/04/1954","10/06/1987","16/05/1990",
+             "12/11/1980","01/01/1997","01/01/1998","01/01/1999")
>  # Proper conversion to class "Date":
>  birth.dat <- as.Date( birth, format="%d/%m/%Y" )
>  # Converson of character to class "cal.yr"
>  bt.yr <- cal.yr( birth, format="%d/%m/%Y" )
>  # Back to class "Date":
>  bt.dat <- as.Date( bt.yr )
>  # Numerical calculation of days since 1.1.1970:
>  days <- Days <- (bt.yr-1970)*365.25
>  # Blunt assignment of class:
>  class( Days ) <- "Date"
>  # Then data.frame() to get readable output of results:
>  data.frame( birth, birth.dat, bt.yr, bt.dat, days, Days, round(Days) )
       birth  birth.dat    bt.yr     bt.dat   days       Days round.Days.
1 14/07/1852 1852-07-14 1852.535 1852-07-14 -42904 1852-07-14  1852-07-14
2 01/04/1954 1954-04-01 1954.246 1954-04-01  -5754 1954-03-31  1954-04-01
3 10/06/1987 1987-06-10 1987.437 1987-06-10   6369 1987-06-10  1987-06-10
4 16/05/1990 1990-05-16 1990.370 1990-05-16   7440 1990-05-15  1990-05-16
5 12/11/1980 1980-11-12 1980.864 1980-11-12   3968 1980-11-11  1980-11-12
6 01/01/1997 1997-01-01 1997.001 1997-01-01   9862 1997-01-01  1997-01-01
7 01/01/1998 1998-01-01 1998.000 1998-01-01  10227 1998-01-01  1998-01-01
8 01/01/1999 1999-01-01 1998.999 1999-01-01  10592 1998-12-31  1999-01-01
> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>