.emacs.d/doc/emacs-org-babel-tutorial.org

Notes on “Babel: Introduction”

• Source Code Execution
  • Capturing the Results of Code Evaluation
  • Session-based Evaluation
  • Arguments to Code Blocks
  • In-line Code Blocks
  • Code Block Body Expansion
  • A Meta-programming Language for Org-mode
  • Using Code Blocks in Org Tables
    • Example 1: Data Summaries Using R
    • Example 2: Babel Test Suite
• The Library of Babel
• Literate Programming
• Reproducible Research

Tutorial from http://orgmode.org/worg/org-contrib/babel/intro.html

Source Code Execution

  (print "Hello, There!")

Hello, There!

  echo "This file takes up `du -h emacs-org-babel-tutorial.org | sed 's/\([0-9k]*\)[ ]*emacs-org-babel-tutorial.org/\1/'`"

This file takes up 4.0K

  words <- tolower(scan("emacs-org-babel-tutorial.org", what="", na.strings=c("|",":")))
  t(sort(table(words[nchar(words) > 3]), decreasing=TRUE)[1:10])

#+begin_src	#+end_src	#+results:	date	plus	today's	:results	hello,	import	is")
5	5	4	3	3	3	2	2	2	2

Capturing the Results of Code Evaluation

  import time
  print("Hello, today's date is %s" % time.ctime())
  print("Two plus two is")
  return 2 + 2

4

  import time
  print("Hello, today's date is %s" % time.ctime())
  print("Two plus two is")
  2 + 2

Hello, today's date is Sun Jun 26 16:04:36 2016
Two plus two is

Session-based Evaluation

Have a look into Emacs Speaks Statistics

Arguments to Code Blocks

  return x*x

36

1	2	3	4	5	6	7	8	9	10
2	4	6	8	10	12	14	16	18	20

  (defun fibonacci (n)
    (if (or (= n 0) (= n 1))
        n
      (+ (fibonacci (- n 1))
         (fibonacci (- n 2)))))

  (mapcar (lambda (row)
            (mapcar #'fibonacci row))
          fib-inputs)

1	1	2	3	5	8	13	21	34	55
1	3	8	21	55	144	377	987	2584	6765

In-line Code Blocks

In-line code can be call without header arguments (like so:

date

) or with header arguments (like so:

return 10 + 10

).

Code Block Body Expansion

Preview: C-c C-v v, bound to org-babel-expand-src-block

username	john-doe
password	abc123

(setq my-special-username (first (first data)))
(setq my-special-password (first (second data)))

A Meta-programming Language for Org-mode

  cd ~ && du -sc * | grep -v total

538604	Desktop
77332656	Documents
1206668	Mail
8	News

  pie(dirs[,1], labels = dirs[,2])

Note: the syntax #+name: directory-pie-chart(dirs=directories) did not work.

Using Code Blocks in Org Tables

Example 1: Data Summaries Using R

  runif(n=5, min=0, max=1)

  colMeans(x)

mean
0.574235895462334

Example 2: Babel Test Suite

No notes

The Library of Babel

Does not do what I expected …

Literate Programming

Tangling with C-c C-v t.

Reproducible Research