Chapter 6 – Going on a Date with R

 
# Chapter 6 - Going on a Date with R
 
# Working with Dates
 
xd <- as.Date("2012-07-27")
xd
str(xd)
weekdays(xd)
xd + 7
xd + 0:6
weekdays(xd + 0:6)
 
startDate <- as.Date("2012-01-01")
xm <- seq(startDate, by="2 months", length.out=6)
xm
 months(xm)
quarters(xm)
 
Sys.localeconv()
 
as.Date("27 July 2012", format="%d %B %Y")
 
as.Date("27/7/12", format="%d/%m/%y")
 
# Adding Time Information to Dates
 
apollo <- "July 20, 1969, 20:17:39"
apollo.fmt <- "%B %d, %Y, %H:%M:%S"
xct <- as.POSIXct(apollo, format=apollo.fmt, tz="UTC")
xct
 
format(xct, "%d/%m/%y")
format(xct, "%S minutes past %I %p, on %d %B %Y")
 
# Performing Operations on Dates and Times
 
## Addition and subtraction
 
24*60*60
xct + 7*86400
xct + 3*60*60
xct - 7*86400
as.Date(xct) - 7
 
## Comparison of dates
 
Sys.time()
Sys.time() < xct
 
dec.start <- as.POSIXct("1950-01-01")
dec <- seq(dec.start, by="10 years", length.out=4)
dec
dec > xct
 
## Extraction
 
xlt <- as.POSIXlt(xct)
xlt
xlt$year
xlt$mon
unclass(xlt)

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