Author Archives: Thomas Cokelaer

Allocation 2D arrays in C (and freeing memory)

Posted on October 6, 2011 by Thomas Cokelaer

By convention, when dealing with 2D array, the first dimension refer to the rows, and the second to the columns. To create a 2D array (double pointer) in C, you first create a 1D array of pointers (rows), and then, … Continue reading →

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RPy2 substitute function does not work

Posted on September 28, 2011 by Thomas Cokelaer

I’m using rpy2 to call R package from Python, which works pretty well most of the time. Yet, I’ve encountered an issue with the R function called substitute that do not behave as expected when called from rpy2. Consider the … Continue reading →

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Set the default printer under linux

Posted on September 22, 2011 by Thomas Cokelaer

If you want to set the default printer, you can use the command line interface and type: export PRINTER=printer-nameexport PRINTER=printer-name If you want to set the default printer permanently, and if your shell is bash (most common by default), you … Continue reading →

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super() function in Python raises a TypeError

Posted on September 22, 2011 by Thomas Cokelaer

Playing with class inheritance, I came across an unexpected behavior of super() function, which is used in the inheritance process. Consider this simple example of a class MyGraph thah inherits from a DiGraph class from networkx: import networkx as nx … Continue reading →

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a2ps usage

Posted on September 21, 2011 by Thomas Cokelaer

a2ps is a unix tool that ease the formatting of text files before printing. a2ps inputfile -o output.psa2ps inputfile -o output.ps Print code that span over more than 80 columns. You will need to decrease the font size (-f 7), … Continue reading →

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How to generate a PDF reference of an R package

Posted on September 19, 2011 by Thomas Cokelaer

If you have the Rd files in a man directory, then in a shell command, you can use this command: R CMD Rd2dvi –pdf –title=’Test of foo’ -o /tmp/foo.pdf man/*.RdR CMD Rd2dvi –pdf –title=’Test of foo’ -o /tmp/foo.pdf man/*.Rd

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HTML password protected

Posted on September 14, 2011 by Thomas Cokelaer

Password protecting a website (or a sub directory within a website) can be done easily thanks to two special files called .htaccess and .htpasswd First, in the directory that you want to be protected, copy and paste the following code … Continue reading →

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pdf2ps font issues

Posted on September 13, 2011 by Thomas Cokelaer

Sometimes, when converting a PDF file to a PS file using ps2pdf, some fuzzy fonts may appear. A solution is to provide the fonts within the documents by using: pdf2ps -dEmbedAllFonts=true <input> <output>pdf2ps -dEmbedAllFonts=true <input> <output>

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scp does not work: wrong bashrc

Posted on September 13, 2011 by Thomas Cokelaer

When I tried to use scp to copy a file on a distant machine: scp -v filename username@xxx.xxx.xxx:/home/usernamescp -v filename username@xxx.xxx.xxx:/home/username it looked as if the SCP command works but the file is not copied. The interactive option (-v) does … Continue reading →

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How to resize images with awk and convert

Posted on September 11, 2011 by Thomas Cokelaer

If photos in a directory are too large, you may want to use a script to automatically convert all the files into another format. AWK and convert tools can help you. The following command should convert all the files with … Continue reading →

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