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Support for measurement units in R vectors, matrices and arrays: automatic propagation, conversion, derivation and simplification of units; raising errors in case of unit incompatibility. Compatible with the POSIXct, Date and difftime classes. Uses the UNIDATA udunits library and unit database for unit compatibility checking and conversion.


Documentation is provided in an R Journal publication. Cite this package as:

  • Edzer Pebesma, Thomas Mailund and James Hiebert (2016). “Measurement Units in R.” The R Journal, 8 (2), 486–494. DOI: 10.32614/RJ-2016-061

The main units vignette derives from this manuscript and is kept up to date with the package development.

What it does

Package units provides measurement units for R vectors: conversion, derivation, simplification and error checking:

(spd1 = set_units(1:5, m/s))
# Units: m/s
# [1] 1 2 3 4 5
(spd2 = set_units(1:5, km/h))
# Units: km/h
# [1] 1 2 3 4 5
spd1 + spd2                   # automatic conversion
# Units: m/s
# [1] 1.277778 2.555556 3.833333 5.111111 6.388889
spd1 * spd2                   # unit derivation
# Units: km*m/h/s
# [1]  1  4  9 16 25
spd1 * set_units(10, s) # unit simplification
# Units: m
# [1] 10 20 30 40 50
spd1 + set_units(10, s) # error checking
#   cannot convert s into m/s


Install the release version from CRAN:

The installation of the development version from GitHub requires, e.g., the remotes package:


If the installation fails due to a missing udunits2 system library, either install it e.g. on Ubuntu or Debian by

sudo apt-get install libudunits2-dev

on Fedora or RHEL/CentOS with

sudo dnf install udunits2-devel

or on MacOS with

brew install udunits

or equivalent in your distribution. Alternatively, install it from the sources by downloading the latest version from UDUNITS downloads, and executing the following commands in the download directory:

tar zxf udunits-<version>.tar.gz
cd ./udunits-<version>/
sudo make install
sudo ldconfig

Then, retry the installation of units.