nanotime
Nanosecond Time Resolution for R
Motivation
R has excellent tools for dates and times. The Date
and POSIXct
classes (as well as the 'wide'
representation in POSIXlt
) are versatile, and a lot of useful tooling has been built around them.
However, 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) chrono
type.
Demo
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
Examples
Simple Parsing and Arithmetic
R> x <- nanotime("1970-01-01T00:00:00.000000001+00:00")
R> print(x)
integer64
[1] 1
R> format(x)
[1] "1970-01-01T00:00:00.000000001+00:00"
R> x <- x + 1
R> print(x)
integer64
[1] 2
R> format(x)
[1] "1970-01-01T00:00:00.000000002+00:00"
R>
Vectorised
R> options("width"=60)
R> v <- nanotime(Sys.time()) + 1:5
R> v
integer64
[1] 1481505724483583001 1481505724483583002
[3] 1481505724483583003 1481505724483583004
[5] 1481505724483583005
R> format(v)
[1] "2016-12-12T01:22:04.483583001+00:00"
[2] "2016-12-12T01:22:04.483583002+00:00"
[3] "2016-12-12T01:22:04.483583003+00:00"
[4] "2016-12-12T01:22:04.483583004+00:00"
[5] "2016-12-12T01:22:04.483583005+00:00"
R>
Use with zoo
R> z <- zoo(cbind(A=1:5, B=5:1), v)
R> options("nanotimeFormat"="%H:%M:%E*S") ## override default
R> z
A B
01:47:55.812513001 1 5
01:47:55.812513002 2 4
01:47:55.812513003 3 3
01:47:55.812513004 4 2
01:47:55.812513005 5 1
R>
Use with data.table
R> library(data.table)
R> library(bit64) # register some print methods for integer64
R> dt <- data.table(cbind(A=1:5, B=5:1), v)
R> fwrite(dt, file="datatableTest.csv") # write out
R> dtcheck <- fread("datatableTest.csv") # read back, need to re-set class
R> dtcheck[, v:=nanotime(v)] # need to re-class as nanotime
Use with data.frame
This requires version 0.0.2 or later.
R> df <- data.frame(cbind(A=1:5, B=5:1), v=v)
Technical Details
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.
Status
The package is in the very early stages. Expect changes, maybe even breaking ones. But the package has some tests, and code coverage.
See the issue tickets for an up to date list of potentially desirable, possibly planned, or at least discussed items.
Installation
The package is on CRAN and can be installed via a standard
install.packages("nanotime")
whereas in order to install development versions a
remotes::install_github("eddelbuettel/nanotime") # dev version
should suffice.
Author
Dirk Eddelbuettel
License
GPL (>= 2)