oce (version 0.9-18)

numberAsPOSIXct: Convert a numeric time to a POSIXct time

Description

Convert a numeric time to a POSIXct time

Usage

numberAsPOSIXct(t, type=c("unix", "matlab", "gps", "argo",
                          "ncep1", "ncep2", "sas", "spss", "yearday"), tz="UTC")

Arguments

t

an integer corresponding to a time, in a way that depends on type.

type

the type of time (see Details).

tz

a string indicating the time zone, used only for unix and matlab times, since GPS times are always referenced to the UTC timezone.

Value

• A POSIXct time vector.

Details

There are many varieties, according to the value of type as defined below.

• "unix"employs Unix times, measured in seconds since the start of the year 1970.
• "matlab"employs Matlab times, measured in days since what MathWorks [1] calls ``January 0, 0000'' (i.e.ISOdatetime(0, 1, 1, 0, 0, 0)in R notation).
• "gps"employs the GPS convention. For this,tis a two-column matrix, with the first column being the the GPS "week" (referenced to 1999-08-22) and the second being the GPS "second" (i.e. the second within the week).
• "argo"employs Argo times, measured in days since the start of the year 1900.
• "ncep1"employs NCEP times, measured in hours since the start of the year 1800.
• "ncep2"employs NCEP times, measured in days since the start of the year 1. (Note that, for reasons that are unknown at this time, a simple R expression of this definition is out by two days compared with the UDUNITS library, which is used by NCEP. Therefore, a two-day offset is applied. See [2,3].)
• "sas"employs SAS times, indicated bytype="sas", have origin at the start of 1960.
• "spss"employs SPSS times, in seconds after 1582-10-14.
• "yearday"employs a convention in whichtis a two-column matrix, with the first column being the year, and the second the yearday (starting at 1 for the first second of January 1, to match the convention used by Sea-Bird CTD software).

References

[1] Matlab times: http://www.mathworks.com/help/matlab/ref/datenum.html

[2] NCEP times: http://www.esrl.noaa.gov/psd/data/gridded/faq.html#3

[3] problem with NCEP times: https://github.com/dankelley/oce/issues/738

See Also

numberAsHMS

Examples

numberAsPOSIXct(0)                     # unix time 0
numberAsPOSIXct(1, type="matlab")      # matlab time 1
numberAsPOSIXct(cbind(566,345615), type="gps") # Canada Day
numberAsPOSIXct(cbind(2013, 0), type="yearday") # start of 2013