knitR and LaTeX for bioinformatics

knitR is a great way of dynamically generating reports, and ensuring that they're always based on up-to-date data. Having the reporting closely tied to the data and code that generated it is one of the tenets of reproducible research. In bioinformatics, one often finds oneself repeatedly generating figures, graphs, etc, for multiple labels (eg. probes, genes, etc). knitR is a great fit for this.

I had some difficulty finding the best way of iterating and generating multiple reports, and the code below is the best way I have found so far.

The following example code iterates over each label in a data.frame, and generates a separate .pdf for each. In a real scenario, each label could be a gene, and we could pull out whatever data/tables/figures we wanted.

Note that you may need to install some R libraries for this code to work:

• ggplot2
• xtable
• knitr

Below is example code to do this. A control R-script. Adjust the path in the knit2pdf command, put this in a file, make it executable, and run it: The actual knitR file is below. This is essentially a LaTeX file with blobs (called "chunks" in knitR) of R in it that are evaluated and their output included in the final document, as desired. I saw the xtable technique on this blog.