> library(data.table)

data.table 1.14.0 using 1 threads (see ?getDTthreads).  Latest news: r-datatable.com

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This installation of data.table has not detected OpenMP support. It should still work but in single-threaded mode.

This is a Mac. Please read https://mac.r-project.org/openmp/. Please engage with Apple and ask them for support. Check r-datatable.com for updates, and our Mac instructions here: https://github.com/Rdatatable/data.table/wiki/Installation. After several years of many reports of installation problems on Mac, it's time to gingerly point out that there have been no similar problems on Windows or Linux.

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> year<-rep(c(2012:2015), each=12000000)

> month<-rep(rep(c(1:12), each=1000000), 4)

> value<-runif(48000000)

> DataFrame<-data.frame(year, month, value)

> DataTable<-as.data.table(DataFrame)

> system.time(DataFrame[DataFrame$year==2012, ])

   user  system elapsed 

  0.556   0.116   0.702 

> system.time(DataTable[DataTable$year==2012, ])

   user  system elapsed 

  0.234   0.074   0.317 

# 칼럼이 키 값으로 설정된 경우 자동 오름차순 정렬

> setkey(DataTable, year)

# 키 값으로 설정된 칼럼과 J 표현식을 사용한 검색 시간 측정

> system.time(DataTable[J(2012)])

   user  system elapsed 

  0.282   0.015   0.298