DateNum {RcppTemplate} | R Documentation |
Various date utility functions that return date serial numbers used by R, Excel, Julian system, etc.
numJulian(date) numExcelPC(date) numExcelMac(date) numWeekday(date)
date |
a date object of class Date or POSIXt |
The Julian day number is a standardized measure of time starting from a
distant date in the past. The starting date for R's Date type,
1/1/1970, has Julian day number ROffset
(2440588).
The function numWeekday()
returns the weekday corresponding to a
particular date: Sun=0, Mon=1, etc. This is computed from the Julian
day number as: (JDN + 1) modulo 7.
The default date represention used by Excel on a PC is returned by
numExcelPC()
, and the default representation used by Excel
on a Mac is returned by numExcelMac()
. To get the time right
these functions should be applied to POSIXt type date-times; otherwise
the time-of-day component is truncated.
Returns the serial number that applies. The julian day number is always an integer, but the other serial numbers normally include a fractional part to represent fractions of a day (down to the fraction of a second).
Dominick Samperi
d <- as.Date('1970-01-01') numJulian(d) # returns 2440588 numR(d) # returns 0 numWeekday(d) # returns 4 (Thursday) dt <- Sys.time() # current date and time numJulian(dt) # a large integer (fractional part dropped) numExcelPC(dt) # includes fractional days