UC Business Analytics R Programming Guide

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Creating Date Sequences

To create a sequence of dates we can leverage the seq() function. As with numeric vectors, you have to specify at least three of the four arguments (from, to, by, and length.out).

seq(as.Date("2010-1-1"), as.Date("2015-1-1"), by = "years")
## [1] "2010-01-01" "2011-01-01" "2012-01-01" "2013-01-01" "2014-01-01"
## [6] "2015-01-01"

seq(as.Date("2015/1/1"), as.Date("2015/12/30"), by = "quarter")
## [1] "2015-01-01" "2015-04-01" "2015-07-01" "2015-10-01"

seq(as.Date('2015-09-15'), as.Date('2015-09-30'), by = "2 days")
## [1] "2015-09-15" "2015-09-17" "2015-09-19" "2015-09-21" "2015-09-23"
## [6] "2015-09-25" "2015-09-27" "2015-09-29"

Using the lubridate package is very similar. The only difference is lubridate changes the way you specify the first two arguments in the seq() function.

library(lubridate)

seq(ymd("2010-1-1"), ymd("2015-1-1"), by = "years")
## [1] "2010-01-01 UTC" "2011-01-01 UTC" "2012-01-01 UTC" "2013-01-01 UTC"
## [5] "2014-01-01 UTC" "2015-01-01 UTC"

seq(ymd("2015/1/1"), ymd("2015/12/30"), by = "quarter")
## [1] "2015-01-01 UTC" "2015-04-01 UTC" "2015-07-01 UTC" "2015-10-01 UTC"

seq(ymd('2015-09-15'), ymd('2015-09-30'), by = "2 days")
## [1] "2015-09-15 UTC" "2015-09-17 UTC" "2015-09-19 UTC" "2015-09-21 UTC"
## [5] "2015-09-23 UTC" "2015-09-25 UTC" "2015-09-27 UTC" "2015-09-29 UTC"

Creating sequences with time is very similar; however, we need to make sure our date object is POSIXct rather than just a Date object (as produced by as.Date):

seq(as.POSIXct("2015-1-1 0:00"), as.POSIXct("2015-1-1 12:00"), by = "hour")
##  [1] "2015-01-01 00:00:00 EST" "2015-01-01 01:00:00 EST"
##  [3] "2015-01-01 02:00:00 EST" "2015-01-01 03:00:00 EST"
##  [5] "2015-01-01 04:00:00 EST" "2015-01-01 05:00:00 EST"
##  [7] "2015-01-01 06:00:00 EST" "2015-01-01 07:00:00 EST"
##  [9] "2015-01-01 08:00:00 EST" "2015-01-01 09:00:00 EST"
## [11] "2015-01-01 10:00:00 EST" "2015-01-01 11:00:00 EST"
## [13] "2015-01-01 12:00:00 EST"

# with lubridate
seq(ymd_hm("2015-1-1 0:00"), ymd_hm("2015-1-1 12:00"), by = "hour")
##  [1] "2015-01-01 00:00:00 UTC" "2015-01-01 01:00:00 UTC"
##  [3] "2015-01-01 02:00:00 UTC" "2015-01-01 03:00:00 UTC"
##  [5] "2015-01-01 04:00:00 UTC" "2015-01-01 05:00:00 UTC"
##  [7] "2015-01-01 06:00:00 UTC" "2015-01-01 07:00:00 UTC"
##  [9] "2015-01-01 08:00:00 UTC" "2015-01-01 09:00:00 UTC"
## [11] "2015-01-01 10:00:00 UTC" "2015-01-01 11:00:00 UTC"
## [13] "2015-01-01 12:00:00 UTC"