R has excellent tools for dates and times. The
POSIXct classes (as well as the ‘wide’ representation in
POSIXlt) are versatile, and a lot of useful tooling has been built around them.
POSIXct is implemented as a
double with fractional seconds since the epoch. Given the 53 bits accuracy, it leaves just a bit less than microsecond resolution. Which is good enough for most things.
But more and more performance measurements, latency statistics, … are now measured more finely, and we need nanosecond resolution. For which commonly an
integer64 is used to represent nanoseconds since the epoch.
And while R does not have a native type for this, the bit64 package by Jens Oehlschlägel offers a performant one implemented as a lightweight S3 class. So this package uses this
integer64 class, along with two helper functions for parsing and formatting, respectively, at nano-second resolution from the RcppCCTZ package which wraps the CCTZ library from Google. CCTZ is a modern C++11 library extending the (C++11-native)
In addition to the point-in-time type
nanotime, this package also provides an interval type
nanoival which may have open or closed start/end, a period type
nanoperiod that is a human representation of time, such as day, month, etc., and a duration type
nanoduration. These types are similar to what the lubridate package proposes.
Set and arithmetic operations on these types are available. All functionality is designed to correctly handle instances across different time zones. Because these temporal types are based on R built-in types, most functions have an efficient implementation and the types are suitable for use in
nanotime is also a better choice than the native
POSIXct in most of the cases where fractional seconds are needed because it avoids floating point issues.
Package documentation, help pages, a vignette, and more are available here.
See the included demo script nanosecondDelayExample.R for a (completely simulated and hence made-up) study of network latency measured in nanoseconds resulting in the figure below
R> options("width"=60) R> v <- nanotime(Sys.time()) + 1:5 R> v integer64  1481505724483583001 1481505724483583002  1481505724483583003 1481505724483583004  1481505724483583005 R> format(v)  "2016-12-12T01:22:04.483583001+00:00"  "2016-12-12T01:22:04.483583002+00:00"  "2016-12-12T01:22:04.483583003+00:00"  "2016-12-12T01:22:04.483583004+00:00"  "2016-12-12T01:22:04.483583005+00:00" R>
The bit64 package (by Jens Oehlschlägel) supplies the
integer64 type used to store the nanosecond resolution time as (positive or negative) offsets to the epoch of January 1, 1970. The RcppCCTZ package supplies the formatting and parsing routines based on the (modern C++) library CCTZ from Google.
The package is by now fairly mature, has been rewritten once (to go from S3 to S4) and has recently received a sizeable feature extension. There may still be changes, though there should generally never be breaking ones. The package also has an extensive test suite, and very good code coverage.
See the issue tickets for an up to date list of potentially desirable, possibly planned, or at least discussed items.
The package is on CRAN and can be installed via a standard
whereas in order to install development versions a
Dirk Eddelbuettel and Leonardo Silvestri
GPL (>= 2)