ct: Convertion to POSIXct

In onlineforecast: Forecast Modelling for Online Applications

Convertion to POSIXct

Description

The object is converted into POSIXct with tz="GMT".

Usage

ct(object, ...)

## S3 method for class 'character'
ct(object, tz = "GMT", ...)

## S3 method for class 'POSIXct'
ct(object, tz = NA, duplicatedadd = NA, ...)

## S3 method for class 'POSIXlt'
ct(object, tz = NA, duplicatedadd = NA, ...)

## S3 method for class 'numeric'
ct(object, ...)

Arguments

object	The object to convert can be: character, numeric, POSIXct or POSIXlt
...	Arguments to be passed to methods.
tz	Timezone. If set, then the time zone will be changed of the object.
duplicatedadd	Seconds to be added to duplicated time stamps, to mitigate the problem of duplicated timestamps at the shift to winter time. So the second time a time stamp occurs (identified with duplicated) then the seconds will be added.

Details

A simple helper, which wraps as.POSIXct' and sets the time zone to "GMT" per default.

Value

An object of class POSIXct

Methods

- ct.character: Simply a wrapper for as.POSIXct with default tz

- ct.POSIXct: Changes the time zone of the object if tz is given.

- ct.POSIXlt: Converts to POSIXct.

- ct.numeric: Converts from UNIX time in seconds to POSIXct with tz as GMT.

Examples

# Create a POSIXct with tz="GMT"
ct("2019-01-01")
class(ct("2019-01-01"))
ct("2019-01-01 01:00:05")


# Convert to POSIXct
class(ct(as.POSIXlt("2019-01-01")))

# To seconds and back again
ct(as.numeric(1000, units="sec"))


# --------
# Convert character of time which has summer time leaps
# Example from CET (with CEST which is winter time)
# 
# The point of shifting to and from summer time:
# DST Start (Clock Forward)	DST End (Clock Backward)
# Sunday, March 31, 02:00	Sunday, October 27, 03:00

# --------
# From to winter time to summer time
txt <- c("2019-03-31 01:00",
         "2019-03-31 01:30",
         "2019-03-31 03:00",
         "2019-03-31 03:30")
x <- ct(txt, tz="CET")
x
ct(x, tz="GMT")

# BE AWARE of this conversion of the 02:00: to 02:59:59 (exact time of shift) will lead to a
# wrong conversion
txt <- c("2019-03-31 01:30",
         "2019-03-31 02:00",
         "2019-03-31 03:30")
x <- ct(txt, tz="CET")
x
ct(x, tz="GMT")
# Which a diff on the time can detect, since all steps are not equal
plot(diff(ct(x, tz="GMT")))

# --------
# Shift to winter time is more problematic
# It works like this 
txt <- c("2019-10-27 01:30",
         "2019-10-27 02:00",
         "2019-10-27 02:30",
         "2019-10-27 03:00",
         "2019-10-27 03:30")
x <- ct(txt, tz="CET")
x
ct(x, tz="GMT")

# however, timestamps can be given like this
txt <- c("2019-10-27 01:30",
         "2019-10-27 02:00",
         "2019-10-27 02:30",
         "2019-10-27 02:00",
         "2019-10-27 02:30",
         "2019-10-27 03:00",
         "2019-10-27 03:30")
x <- ct(txt, tz="CET")
x
ct(x, tz="GMT")
# Again can be detected, since all steps are not equal
plot(diff(ct(x, tz="GMT")))
# This can be fixed by (note that it can go wrong, e.g. with gaps around convertion etc.)
ct(x, tz="GMT", duplicatedadd=3600)

onlineforecast documentation built on Oct. 12, 2023, 5:15 p.m.