A function to create a vector of time-based objects suitable for indexing an xts object, given a string conforming to the ISO 8601 time and date standard for range-based specification. The resultant series can be of any class supported by xts, including POSIXct, Date, chron, timeDate, yearmon, and yearqtr.
timeBasedRange creates a vector of length 1 or 2
as seconds since the epoch (1970-01-01) for use
internally.
timeBasedSeq(x, retclass = NULL, length.out = NULL)timeBasedRange(x, ...)
A sequence or range of time-based objects.
If retclass is NULL, the result is a named
list of from, to, by and length.out.
a string representing the time-date range desired
the return class desired
passed to seq internally
unused
Jeffrey A. Ryan
Designed to provide uniform creation of valid time-based objects for use within xts, the interface conforms (mostly) to the ISO recommended format for specifying ranges.
In general, the format is a string specifying a time and/or date from, to, and optionally by delineated by either ‘"/"’ or ‘"::"’.
The first argument need not be quoted, as it is converted internally if need be.
The general form is from/to/by or from::to::by, where to and by are optional if the length.out arg is specified.
The from and to elements of the string
must be left-specified with respect to the standard
CCYYMMDD HHMMSS form. All dates-times
specified will be set to either the earliest point (from)
or the latest (to), given the level of specificity.
For example ‘1999’ in the from field would set the start to the beginning of 1999. The opposite occurs in the to field.
The level of detail in the request is interpretted as the level of detail in the result. The maximum detail of either from or to is the basis of the sequence, unless the optional by element is specified, which will be covered later.
To request a yearly series, it is only necessary to
use ‘"1999/2008"’. Alternately, one could
request a monthly series (returned by default as
class yearmon) with ‘"199901/2008"’ or
‘"1999-01/2008"’, or even ‘"1999/2008-01"’.
As the level of granularity increases, so does the
resultant sequence granularity - as does its length.
Using the optional third by field (the third
delimited element to the string), will override the
granularity intepretation and return the requested
periodicity. The acceptable arguments include
Y for years, m for months, d for
days, H for hours, M for minutes and S for
seconds.
International Organization for Standardization: ISO 8601 https://www.iso.org
timeBased, xts
timeBasedSeq('1999/2008')
timeBasedSeq('199901/2008')
timeBasedSeq('199901/2008/d')
timeBasedSeq('20080101 0830',length=100) # 100 minutes
timeBasedSeq('20080101 083000',length=100) # 100 seconds
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