## Wednesday, 18 May 2011

### Removing N first characters from each line in a file

I recently had to remove the 5 first characters from each line in a text file; it was a source code file copied from the internet with the line numbers included. I found a nice way to do this in a forum post:

sed -i 's/$$.\{5\}$$//' file.m

Here, the "sed" function of the Linux command line is used with the -i (for "in place") switch to remove the 5 first characters from each line in the file "file.m". It looks a bit messy, but it works.

## Wednesday, 4 May 2011

### Using LaTeX in Inkscape Drawings

I use Inkscape to draw all my vector graphics. I often use these graphics in combination with PdfLaTeX to write papers and Beamer presentations. However, one of the things I have been struggling with is how to include greek letters and mathematical formulas in the graphics. One simple solution for displaying Greek letters is to use the corresponding unicode. For example, to display the letter gamma, create a text box, press Ctrl+U, and enter <03B3>. However, the character will (usually) not be available in the same font as the LaTeX document, and it is also hard to write anything more complex than single characters.

It was not until today that I found out that Inkscape actually has a export option that solves this problem quite nicely. This is documented very nicely here. To create a drawing with LaTeX elements, simply enter the LaTeX code in a text box, export as PDF, and cross the box in the PDF export options. This will export the graphics to a PDF file and the text to a separate .tex file, which can then be included in the LaTeX document using this syntax (or similar):

\begin{figure}
\centering
\def\svgwidth{\columnwidth}
\includesvg{image}
\end{figure}

where the file name of the exported graphic is "image". Note that no additional packages are needed. Consult the documentation for more details.

## Tuesday, 3 May 2011

### Spell checking LaTeX documents

Spell checking a LaTeX document is different from spell checking a plain text document, since the LaTeX document contains commands that should be ignored by the spell checker. For example, consider this command for including a figure with a caption:

\begin{figure}
\centering
\includegraphics[width = 7cm]{image1}
\caption{Focused image of piont scatterer.}
\end{figure}

Here, a spell checker should not suggest changing "\includegraphics" to "include graphics", but it should suggest changing the misspelled "piont" in the caption to "point". Luckily, there are spell checkers that interpret LaTeX commands, and I am currently using one of them, Aspell. In Linux, Aspell is easily installed by the following commands:

apt-get install aspell
apt-get install aspell-en

which installs both the program and the english dictionary. To spell check a LaTeX file called paper.tex on the command line, type

aspell -c paper.tex

Note that Aspell (and its relative Ispell) can also be used at runtime by text processing programs like Kile.