data.table

data.table provides a high-performance version of base R's data.frame with syntax and feature enhancements for ease of use, convenience and programming speed.

Why data.table ?

• concise syntax: fast to type, fast to read
• fast speed
• memory efficient
• careful API lifecycle management
• community
• feature rich

Features

• fast and friendly delimited file reader: ?fread, see also convenience features for small data
• fast and feature rich delimited file writer: ?fwrite
• low-level parallelism: many common operations are internally parallelized to use multiple CPU threads
• fast and scalable aggregations; e.g. 100GB in RAM (see benchmarks on up to two billion rows)
• fast and feature rich joins: ordered joins (e.g. rolling forwards, backwards, nearest and limited staleness), overlapping range joins (similar to IRanges::findOverlaps ), non-equi joins (i.e. joins using operators >, >=, aggregate on join ( by=.EACHI ), update on join
• fast add/update/delete columns by reference by group using no copies at all
• fast and feature rich reshaping data: ?dcast (pivot/wider/spread) and ?melt (unpivot/longer/gather)
• any R function from any R package can be used in queries not just the subset of functions made available by a database backend, also columns of type list are supported
• has no dependencies at all other than base R itself, for simpler production/maintenance
• the R dependency is as old as possible for as long as possible, dated April 2014, and we continuously test against that version; e.g. v1.11.0 released on 5 May 2018 bumped the dependency up from 5 year old R 3.0.0 to 4 year old R 3.1.0

Installation

install.packages("data.table") # latest development version (only if newer available) data.table::update_dev_pkg() # latest development version (force install) install.packages("data.table", repos="https://rdatatable.gitlab.io/data.table")

Usage

Use data.table subset [ operator the same way you would use data.frame one, but.

• no need to prefix each column with DT$ (like subset() and with() but built-in)
• any R expression using any package is allowed in j argument, not just list of columns
• extra argument by to compute j expression by group

library(data.table) DT = as.data.table(iris) # FROM[WHERE, SELECT, GROUP BY] # DT [i, j, by] DT[Petal.Width > 1.0, mean(Petal.Length), by = Species] # Species V1 #1: versicolor 4.362791 #2: virginica 5.552000

Getting started

• Introduction to data.table vignette
• Getting started wiki page
• Examples produced by example(data.table)

Cheatsheets

Community

data.table is widely used by the R community. It is being directly used by hundreds of CRAN and Bioconductor packages, and indirectly by thousands. It is one of the top most starred R packages on GitHub, and was highly rated by the Depsy project. If you need help, the data.table community is active on StackOverflow.

Stay up-to-date

• click the Watch button at the top and right of GitHub project page
• read NEWS file
• follow #rdatatable on twitter
• follow #rdatatable on fosstodon
• watch recent Presentations
• read recent Articles

Contributing

Guidelines for filing issues / pull requests: Contribution Guidelines.