diff --git a/README.org b/README.org
index 9e7b1dd..299a7dd 100755
--- a/README.org
+++ b/README.org
@@ -40,3 +40,9 @@ data using the R programming environment
 
  * [[./script/roadoi_package.R]['roadoi']]
  * [[./script/scraping.R]['crul' package - web scraping]]
+
+** Data wrangling with {data.table}
+
+ * [[./doc/datatable_intro.org][Introduction to {data.table}]]
+ * [[./doc/datatable_querying.org][Querying in {data.table}: filter in ~i~ ]]
+ * [[./doc/datatable_querying_j.org][Querying in {data.table}: select in ~j~ ]]
diff --git a/doc/datatable_intro.org b/doc/datatable_intro.org
new file mode 100644
index 0000000..52448c2
--- /dev/null
+++ b/doc/datatable_intro.org
@@ -0,0 +1,90 @@
+#+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
diff --git a/doc/datatable_querying.org b/doc/datatable_querying.org
new file mode 100644
index 0000000..008d366
--- /dev/null
+++ b/doc/datatable_querying.org
@@ -0,0 +1,67 @@
+#+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
+
+
+** Querying data.table
+
+Sintaxis:
+
+ * ~DT[i, j, by]~
+
+Subseting by "i" and "j"
+
+** Subset rows in "i"
+
+#+begin_src R
+  dt1 <- flights[origin == "JFK" & month == 6L]
+  dt1
+#+end_src
+
+Get the first two rows
+
+#+begin_src R
+  flights[1:2]
+#+end_src
+
+#+RESULTS:
+:    year month day dep_delay arr_delay carrier origin dest air_time distance
+: 1: 2014     1   1        14        13      AA    JFK  LAX      359     2475
+: 2: 2014     1   1        -3        13      AA    JFK  LAX      363     2475
+:    hour
+: 1:    9
+: 2:   11
+
+Ordering results of querying
+
+#+begin_src R
+  dt_filt <- flights[order(origin, -dest)]
+  dt_filt
+#+end_src
diff --git a/doc/datatable_querying_j.org b/doc/datatable_querying_j.org
new file mode 100644
index 0000000..b5c1990
--- /dev/null
+++ b/doc/datatable_querying_j.org
@@ -0,0 +1,108 @@
+#+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
+
+
+** Select columns in "j"
+
+This creates a vector
+
+#+begin_src R
+  dt_c <- flights[, arr_delay]
+  head(dt_c)
+#+end_src
+
+To create a data.table, use the function "~list~" or dot "~.~"
+
+#+begin_src R
+  dt_c1 <- flights[, list(arr_delay)]
+  head(dt_c1)
+#+end_src
+
+The selection is wrapped in "~list~", thus, the columns can be
+renamed
+
+#+begin_src R
+  dt_c2 <- flights[, .(delay2arriv = arr_delay, dist = distance)]
+  head(dt_c2)
+#+end_src
+
+#+begin_src R
+  dt_c2a <- flights[, c("arr_delay", "distance")]
+  head(dt_c2a)
+#+end_src
+
+
+#+begin_src R
+  dt_c2b <- flights[, year:day]
+  head(dt_c2b)
+#+end_src
+
+Building new colummns
+
+#+begin_src R
+  head(dt_c2b[, `:=`(time = year -1, # name = value,
+                     pumpkin = month,
+                     tomatoe = day +1)])
+#+end_src
+
+Renaming colummns
+
+#+begin_src R
+  setnames(dt_c2b,
+           c("time", "pumpkin", "tomatoe"),# old names
+           c("time_minus1", "pumpkin_month", "day_plus1")) # new names
+
+  names(dt_c2b)
+#+end_src
+
+#+begin_src R
+  setnames(dt_c2b, toupper) # new names
+  names(dt_c2b)
+#+end_src
+
+Renaming colummns
+
+#+begin_src R
+  setnames(dt_c2b, tolower) # new names
+  names(dt_c2b)
+#+end_src
+
+#+begin_src R
+  dt_c2c <- flights[, -(year:day)]
+  head(dt_c2c)
+#+end_src
+
+Select columns by patterns, e.g., selecting 5 lines form columns having "del"
+characters in the name:
+
+#+begin_src R
+  flights[1:5, names(flights) %like% "del", with = FALSE]
+#+end_src