#+TITLE: Datatable package
#+DATE: 2021-10-26
#+OPTIONS: creator:nil timestamp:nil todo:nil num:nil
#+PROPERTY: header-args:R :results output :session *Rc* :cmdline :tangle yes
#+PROPERTY: header-args:R+ :exports both
#+SETUPFILE: https://fniessen.github.io/org-html-themes/org/theme-readtheorg.setup
#+HTML_HEAD: <style> #content{max-width:1800px;}</style>
#+HTML_HEAD: <style> p{max-width:800px;}</style>
#+HTML_HEAD: <style> li{max-width:800px;}</style>
#+HTML_HEAD: <style> pre.src{background: #f5f5f5;color:black;}</style>
#+HTML_HEAD: <style> .example{background: #fefefa;color:black;}</style>


#+begin_export html
  <div id="subtitle" style="float: center; text-align: center;">
    <p>
      Org document with
      <a href="http://www.r-project.org/">R</a> code
    </p>
    <p>
      <a href="http://www.r-project.org/">
	<img src="http://www.r-project.org/Rlogo.jpg"/>
      </a>
    </p>
  </div>
#+end_export

#+begin_src R :exports code
  rm(list = ls())
#+end_src

** Introduction

#+begin_src R
  library(data.table)
#+end_src


Reading data into R using ~{data.table}~

#+begin_src R :exports code
  url = "https://raw.githubusercontent.com/Rdatatable/data.table/master/vignettes/flights14.csv"
  flights <- fread(url)
#+end_src

#+RESULTS:

#+begin_src R
  names(flights)
#+end_src

#+begin_src R
  flights
#+end_src

#+begin_src R
  nrow(flights)
#+end_src

#+RESULTS:
: [1] 253316

Creating a data.table:

#+begin_src R
  dt <- data.table(col1 = c(1:6),
                   col2 = LETTERS[1:6],
                   col3 = (1))
#+end_src


#+begin_src R
  class(dt)
#+end_src

#+begin_src R
  class(dt$col2)
#+end_src

** Some references to learn more about {data.table}

 * https://cran.r-project.org/web/packages/data.table/vignettes/datatable-intro.html
 * See vignettes in R:
   : > vignette(package="data.table")
 * https://atrebas.github.io/post/2019-03-03-datatable-dplyr/
 * https://rdatatable.gitlab.io/data.table/
 * https://s3.amazonaws.com/assets.datacamp.com/blog_assets/datatable_Cheat_Sheet_R.pdf
 * https://stackoverflow.com/questions/21435339/data-table-vs-dplyr-can-one-do-something-well-the-other-cant-or-does-poorly
 * ~dtplyr~ package:
   * https://github.com/tidyverse/dtplyr