# Extension of `data.frame`

## Documentation for package ‘data.table’ version 1.17.8

- DESCRIPTION file.
- User guides, package vignettes and other documentation.
- Package NEWS.

## Help Pages

A B C D E F G H I J K L M N O P Q R S T U W Y misc

data.table-package | Enhanced data.frame

## -- A --

address | Address in RAM of a variable
all.equal | Equality Test Between Two Data Tables
all.equal.data.table | Equality Test Between Two Data Tables
alloc.col | Over-allocation access
anyDuplicated | Determine Duplicate Rows
anyDuplicated.data.table | Determine Duplicate Rows
as.character.ITime | Integer based date class
as.data.table | Coerce to data.table
as.data.table.array | Coerce to data.table
as.data.table.character | Coerce to data.table
as.data.table.data.frame | Coerce to data.table
as.data.table.data.table | Coerce to data.table
as.data.table.Date | Coerce to data.table
as.data.table.factor | Coerce to data.table
as.data.table.integer | Coerce to data.table
as.data.table.list | Coerce to data.table
as.data.table.logical | Coerce to data.table
as.data.table.matrix | Coerce to data.table
as.data.table.numeric | Coerce to data.table
as.data.table.ordered | Coerce to data.table
as.data.table.xts | Efficient xts to as.data.table conversion
as.Date.IDate | Integer based date class
as.IDate | Integer based date class
as.IDate.Date | Integer based date class
as.IDate.default | Integer based date class
as.ITime | Integer based date class
as.ITime.character | Integer based date class
as.ITime.default | Integer based date class
as.ITime.POSIXlt | Integer based date class
as.ITime.times | Integer based date class
as.list.IDate | Integer based date class
as.matrix | Convert a data.table to a matrix
as.matrix.data.table | Convert a data.table to a matrix
as.POSIXct.IDate | Integer based date class
as.POSIXct.ITime | Integer based date class
as.POSIXlt.ITime | Integer based date class
as.xts.data.table | Efficient data.table to xts conversion
auto-index | Optimisations in data.table
auto-indexing | Optimisations in data.table
autoindex | Optimisations in data.table
autoindexing | Optimisations in data.table

## -- B --

between | Convenience functions for range subsets.

## -- C --

c.IDate | Integer based date class
c.ITime | Integer based date class
cdatatable | data.table exported C routines
chgroup | Faster match of character vectors
chmatch | Faster match of character vectors
chorder | Faster match of character vectors
CJ | Creates a join 'data.table'
class:data.table | S4 Definition for data.table
copy | Copy an entire object
cube | Grouping Set aggregation for data tables
cube.data.table | Grouping Set aggregation for data tables

## -- D --

data.table | Enhanced data.frame
data.table-class | S4 Definition for data.table
data.table-optimize | Optimisations in data.table
data.table.optimize | Optimisations in data.table
datatable-optimize | Optimisations in data.table
datatable-symbols | Special symbols
datatable.optimize | Optimisations in data.table
dcast | Fast dcast for data.table
dcast.data.table | Fast dcast for data.table
droplevels | Fast droplevels
droplevels.data.table | Fast droplevels
duplicated | Determine Duplicate Rows
duplicated.data.table | Determine Duplicate Rows

## -- E --

except | Set operations for data tables

## -- F --

fastorder | Fast row reordering of a data.table by reference
fcase | fcase
fcoalesce | Coalescing missing values
fdroplevels | Fast droplevels
fexcept | Set operations for data tables
fifelse | Fast ifelse
fill | Fill missing values
fintersect | Set operations for data tables
first | First/last item of an object
forder | Fast row reordering of a data.table by reference
forderv | Fast row reordering of a data.table by reference
format.ITime | Integer based date class
format_col | data.table Printing Options
format_col.default | data.table Printing Options
format_col.expression | data.table Printing Options
format_col.POSIXct | data.table Printing Options
format_list_item | data.table Printing Options
format_list_item.default | data.table Printing Options
foverlaps | Fast overlap joins
frank | Fast rank
frankv | Fast rank
fread | Fast and friendly file finagler
froll | Rolling functions
frollapply | Rolling functions
frollmean | Rolling functions
frollsum | Rolling functions
fsetdiff | Set operations for data tables
fsetequal | Set operations for data tables
fsort | Fast parallel sort
funion | Set operations for data tables
fwrite | Fast CSV writer

## -- G --

getDTthreads | Set or get number of threads that data.table should use
getNumericRounding | Change or turn off numeric rounding
GForce | Optimisations in data.table
gforce | Optimisations in data.table
groupingsets | Grouping Set aggregation for data tables
groupingsets.data.table | Grouping Set aggregation for data tables

## -- H --

haskey | Create key on a data.table
hour | Integer based date class

## -- I --

I | Substitute expression
IDate | Integer based date class
IDate-class | Integer based date class
IDateTime | Integer based date class
IDateTime.default | Integer based date class
ifelse | Fast ifelse
indices | Create key on a data.table
inrange | Convenience functions for range subsets.
intersect | Set operations for data tables
is.data.table | Coerce to data.table
is.na.data.table | Enhanced data.frame
isoweek | Integer based date class
ITime | Integer based date class
ITime-class | Integer based date class

## -- J --

J | Creates a join 'data.table'

## -- K --

key | Create key on a data.table

## -- L --

lag | Fast lead/lag for vectors and lists
last | First/last item of an object
Last.updated | Number of rows affected by last update
lead | Fast lead/lag for vectors and lists
let | Assignment by reference
like | Convenience function for calling grep.
locf | Fill missing values

## -- M --

mday | Integer based date class
mean.IDate | Integer based date class
mean.ITime | Integer based date class
measure | Specify measure.vars via regex or separator
measurev | Specify measure.vars via regex or separator
melt | Fast melt for data.table
melt.data.table | Fast melt for data.table
merge | Merge two data.tables
merge.data.table | Merge two data.tables
minute | Integer based date class
month | Integer based date class
moving | Rolling functions

## -- N --

na.fill | Fill missing values
na.omit | Remove rows with missing values on columns specified
na.omit.data.table | Remove rows with missing values on columns specified
nafill | Fill missing values
nocb | Fill missing values

## -- O --

openMP | Set or get number of threads that data.table should use
openmp | Set or get number of threads that data.table should use
Ops.data.table | Enhanced data.frame
order | Fast row reordering of a data.table by reference

## -- P --

patterns | Obtain matching indices corresponding to patterns
print.data.table | data.table Printing Options
print.ITime | Integer based date class

## -- Q --

quarter | Integer based date class

## -- R --

rank | Fast rank
rbind | Makes one data.table from a list of many
rbind.data.table | Makes one data.table from a list of many
rbindlist | Makes one data.table from a list of many
rep.IDate | Integer based date class
rep.ITime | Integer based date class
rleid | Generate run-length type group id
rleidv | Generate run-length type group id
roll | Rolling functions
rollapply | Rolling functions
rolling | Rolling functions
rollmean | Rolling functions
rollsum | Rolling functions
rollup | Grouping Set aggregation for data tables
rollup.data.table | Grouping Set aggregation for data tables
round.IDate | Integer based date class
round.ITime | Integer based date class
rounding | Optimisations in data.table
rowid | Generate unique row ids within each group
rowidv | Generate unique row ids within each group
rowwiseDT | Create a data.table row-wise

## -- S --

second | Integer based date class
seq.IDate | Integer based date class
seq.ITime | Integer based date class
set | Assignment by reference
setalloccol | Over-allocation access
setattr | Set attributes of objects by reference
setcoalesce | Coalescing missing values
setcolorder | Fast column reordering of a data.table by reference
setDF | Coerce a data.table to data.frame by reference
setdiff | Set operations for data tables
setdroplevels | Fast droplevels
setDT | Coerce lists and data.frames to data.table by reference
setDTthreads | Set or get number of threads that data.table should use
setequal | Set operations for data tables
setindex | Create key on a data.table
setindexv | Create key on a data.table
setkey | Create key on a data.table
setkeyv | Create key on a data.table
setnafill | Fill missing values
setnames | Set attributes of objects by reference
setNumericRounding | Change or turn off numeric rounding
setops | Set operations for data tables
setorder | Fast row reordering of a data.table by reference
setorderv | Fast row reordering of a data.table by reference
shift | Fast lead/lag for vectors and lists
shouldPrint | For use by packages that mimic/divert auto printing e.g. IRkernel and knitr
SJ | Creates a join 'data.table'
sliding | Rolling functions
special-symbols | Special symbols
split | Split data.table into chunks in a list
split.data.table | Split data.table into chunks in a list
strsplit | strsplit and transpose the resulting list efficiently
subset | Subsetting data.tables
subset.data.table | Subsetting data.tables
substitute | Substitute expression
substitute2 | Substitute expression

## -- T --

tables | Display 'data.table' metadata
test | Test assertions for equality, exceptions and console output
test.data.table | Runs a set of tests.
timetaken | Pretty print of time taken
transpose | Efficient transpose of list
truelength | Over-allocation access
trunc.ITime | Integer based date class
tstrsplit | strsplit and transpose the resulting list efficiently

## -- U --

union | Set operations for data tables
unique | Determine Duplicate Rows
unique.data.table | Determine Duplicate Rows
uniqueN | Determine Duplicate Rows
update_dev_pkg | Perform update of development version of a package

## -- W --

wday | Integer based date class
week | Integer based date class

## -- Y --

yday | Integer based date class
year | Integer based date class
yearmon | Integer based date class
yearqtr | Integer based date class

## -- misc --

%between% | Convenience functions for range subsets.
%chin% | Faster match of character vectors
%flike% | Convenience function for calling grep.
%ilike% | Convenience function for calling grep.
%inrange% | Convenience functions for range subsets.
%like% | Convenience function for calling grep.
%notin% | Convenience operator for checking if an example is not in a set of elements
%plike% | Convenience function for calling grep.
. | Enhanced data.frame
.( | Enhanced data.frame
.() | Enhanced data.frame
.. | Enhanced data.frame
.BY | Special symbols
.EACHI | Special symbols
.GRP | Special symbols
.I | Special symbols
.Last.updated | Number of rows affected by last update
.N | Special symbols
.NATURAL | Special symbols
.NGRP | Special symbols
.SD | Special symbols
:= | Assignment by reference
[.data.table | Enhanced data.frame