Note taking with LaTeX for learning

Summarizing a text book is easy in LaTeX, but sometimes I want to learn the summarized text. Reading the summary over and over again is not very efficient, so I came up with the typical solution, where you can hide the main part of the summary and can check your knowledge by asking yourself questions based on keywords in the margin. Here is an example, where I started summarizing the R package data.table:

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Now I use hide the main text and can ask myself the questions:

  • Express the data.table in SQL-form?
  • How to create a data.table?

Add the following to your latex file (note that I load also the packages lstlisting and some other packages not mentioned here):

Some remarks:

  • I changed the vertical distance of the paragraphs, so it automatically skips a line (if you summarize with lots of text this is probably not a good thing, but if you summarize R commands like in the example, you don’t want to have to add linebreaks after every paragraph.
  • I removed the indent for new paragraphs for the same reason.
  • I added the package color so I can show the margin notes in the color red (using the renewcommand for the marginfont.

In the text you can now add a margin note by adding:

Column guide in Emacs

Many professional editors have a column guide. For example, below you see in the Powershell editor a veritcal line at column 80.

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This marker comes in handy, if you want to print your files. In Emacs I usually check for the column 80 in the status line.

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However, I usually forget to check, and when I print out stuff or publish, I got line breaks where I don’t want them. Passing the 80th column for comments is not a problem, as a simple Ctrl-q forces Emacs to break the lines nicely and add comment symbols at the beginning.

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But after hitting Ctrl-q, Emacs produces this:

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There is, however, a package, that mimics column guide seen in other editors. The package is called “fill-column-indicator”. Installing this package will do the trick. After installing, you only have to add the following lines to your .emacs file:

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I added two hooks, so the column rule appears automatically in Gams and ess.

More information can be found here: http://www.emacswiki.org/emacs/FillColumnIndicator

Using file templates in Emacs

A good practice in modeling is to place information related to the project your are working on, the subject, the data and your personal information like E-mail address at the top of your file. In Emacs you can define skeleton functions that will prompt for the information and put it in the file. Below is an example for a file with as comment symbol “**: (the $Id: $ is for my version control system, that automatically will add the information on the last commit in this line).

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Below you see how to make a function using skeleton. As I don’t want to repeat myself, the function asks as an input the comment symbol(s) that should be used. I now can use the function for different programming languages (R uses “#” , C++ uses two forward slashes, GAMS “*”, etc.). You can add the time and date by using the command “current-time-string”. All other inputs that have skeleton-read in front of it, are also prompted for. If you need the template for your whole project team, you could just make the author and contact field also input-dependent.

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More information can be found at: SkeletonMode. (note that this is part of Emacs since version 22).

PS. The function puts an extra comment symbol at the end (not shown). This is a bug in my function. Any ideas how to get rid of this are welcome.

Using Org-mode to keep track of your project files

For every project I work on I have a org-file. Every file has the following structure:

  • Tasks
  • Repeat
  • Wait
  • Notes
  • Calls
  • Reading

I use remember-mode to capture tasks, notes and calls. Under the heading “Repeat” are tasks that are repeated on a regularly base. Under “Wait” are reminders for things I wait for (like a reply on an e-mail, an order, a call, etc.). These waits are also captured using org-remember (I have written about that in an earlier post). Under the heading “Reading” I have links to papers I am currently reading (using Bibtex; see an earlier post on that).

Sometimes it is nice to have information on the files in one of the project directories, if possible with links. This can be done with org-fstree. Just add (require ‘org-fstree) in your .emacs-file after installing. You now can add the following line somewhere in your org-project file:

#+BEGIN_FSTREE: d:/inbox/Gams

This will give me all the files in the directory d:/inbox/Gams with a direct link (this is my folder for answering questions in the Gams forums).

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You can update this by putting the cursor in this line and hitting C-c C-c. The documentation gives you information on the options:

“#+BEGIN_FSTREE: <dir> :<optionname1> <optionvalue1> :<optionname2> <optionvalue2> …

Options are:

  • :non-recursive t , to suppress recursion into directories
  • :exclude-regexp-name <list of regexp strings> , exclude file/directory names matching either of the given regexp expressions
    • :exclude-regexp-name (“.*\\.pdf$” “.*\\.zip$”), excludes files/directories ending with either “.pdf” or “.zip”
    • :exclude-regexp-name (“^\\.git$“) , excludes files/directories named “.git”
    • – :exclude-regexp-fullpath <list of regexp strings>, same as :exclude-regexp-name but matches absolute path to file/directory
  • :relative-links t , generates relative instead of absolute links
  • :show-only-matches t , only files that are being linked to show up
  • :only-directories t , only directories are listed
  • :only-regular-files t , only regular files are listed
  • :dynamic-update t , [EXPERIMENTAL] dynamically update a subtree on visibility cycling.
  • :links-as-properties t, sets the links as properties Link1, Link2,… for use in column view [Does not work with dynamic-update!]
  • :no-annotations t, suppresses the search and display of file annotations

Following up on Outlook E-Mails in Org-Mode

The combination of Org-Mode and Remember-Mode helps me to organize my projects. One special task category is “WAIT”, if I have to wait for some input from somebody else or waiting for a delivery to arrive. An example is ordering a book at Amazon. As soon as I make the order, I generate a “WAIT” which would look like this

** WAIT [#C] [2014-09-16 Tu] Book on Modeling by Morgan

In this case, I ordered the book on September 9th and it has not a high priority. Once a week I check this category in a customized agenda view which sorts the WAITs according to their priority. If necessary, I take action (for example resending an E-Mail). 

One nuisance is that I use Outlook for my E-Mails and Org-Mode for my tasks.If I send an E-Mail and are waiting for an answer, or if I receive an E-Mail with information on my order, I can’t generate a direct link between the E-Mail and the WAIT-task and I loose time looking for the original E-Mail.

I googled around and found the following solution by John Hilliard here (there is org-outlook, but I did not find a good explanation, how that works). He suggests to write a macro in Outlook that looks like this

The macro gets the unique id for the email message and writes an Org Mode link to that message to the clip board.

Note that in order to write a macro, you have to activate the “Developer” tab in Outook, image

which can be done by right-clicking on the tabs and choosing “Customizing the Ribbon”. After defining the macro, you can add it to the quick access toolbar (same procedure as adding the developer tab), and choose a nice icon

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There might be an error, when running the macro, but you John nicely describes how to get rid of that one:

“When I first ran the macro, I actually got an error saying “Compile error: User-defined type not defined.” That was a little mysterious. In order to fix that error:

Click “Tools” then “References” in the menu.

Check “Microsoft Forms 2.0 Object Library” in the list of available references. 

  • This option wasn’t available to me at first so I clicked “Browse”
  • Then I opened “c:\windows\system32\FM20.DLL”

Then I clicked “OK”

I finally added the code for opening Outlook in my .emacs file.

(defcustom org-outlook-location (w32-short-file-name “c:/Program Files/Microsoft Office 15/root/office15/OUTLOOK.exe”)
  “* Microsoft Outlook 2013 location.”
  :type ‘string
  :group ‘org-outlook)

Now, I can select a message, click on the macro symbol which copies the link, jump to Emacs (I have a script for that) and insert the link. The WAIIT-Task would look like this: image

If I click on the Message-link, Outlook opens the message.

Using Preview for LaTeX documents in Emacs

Editing LaTeX documents with lots of equations can be sometimes hard if you want to refer to the equations in the text. You can use, if you have a big monitor, put the compiled file to the right of your editor, but on a notebook this is not a good option. If you use AucTex in Emacs, you can use the preview mode.

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Here is the text without preview in Emacs And here it is with preview.

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You can set the display options in the Option Group “AucTex” under “Preview Appearance”. One more thing: I always compile to pdf (not dvi). In order to generate the preview, you have to set this option back (C-c C-t C-p).

Automating writing LaTeX papers even further

In an earlier post I wrote on how to use R to produce all kind of figures and tables for a LaTeX paper. This time, I will show, how to automate this process even more.

My work flow consists of a batch file, that runs my model, sends the results to R, produces my tables and figures and sends these to my paper: If I change my model, I just have to run this batch file, and the results in my paper are automatically adjusted. One smaller problem is that I often write in my text on a specific value from a table (for example, the minimum time used). Every time I change my model, I have to check these entries by hand (of course, I could use knitr, but that is on my list for the future and at the moment, I want to keep my R-files separate from my LaTeX files).

Here is a neat trick, to automate this process. Suppose I have calculated the reduction in time in my model and exported the results to R. In my paper I have the following  sentence:

“As you can see in Table 1,in the scenario “Cruising” the reduction in driving time is 12.4%.”

In my R-script, I have the R-Code that produces this value or takes the value from my model results directly. Now I use some simple R-commands to produce a LaTeX file that can be included in my paper:

In my LaTeX-paper, I now just change the sentence to:

This produces the same sentence as before. However, if I change my model, the minimal reduction is changed and automatically adjusted.

Removing extra blank lines in Emacs

If you want to get rid of extra blank lines in your text files, you can use the search and replace commands with regular expressions. However, for whatever reason, this does not work properly on my Windows machine.

Fortunately, I found a nice function definition at stackoverflow which does the job:

http://stackoverflow.com/questions/4419576/delete-extra-blank-lines-in-emacs

Get rid of tabs in Emacs

If you work with other on text files, you often run into the problem that one of the programmers is using tabs set to 4, another to 8 spaces. For this reason, I always save my files without tabs. In Emacs there is a command to do this “untabify-buffer”, but I usually forget to do this.

Searching the internet I found the following code at stackoverflow.com, to do it automatically as soon as you save the file.

You can define your own hooks for other modes.

If you would use the untabify-buffer as a common hook, you can run into problems, because every file will be untabified.