depthq - ccm|mac

I have always been interested with visualisation of data. I like to generate graphs from data. I have some ideas in my head for a while but never got around to actually doing it. Google Finance has a really nice visualisation for tracking stock prices and foreign exchange. So since I am interested in tracking the foreign exchange of the local banks in Malaysia I decided to do a bit of hacking to make my own Google Finance-ish interface to the data. The graph that I render is actually the percentage of change as compared to the forex rate of 4.77.

I've been scraping the foreign exchange data from RHB Bank website for a while and wanted to plot the data into a graph. I looked around a bit for some open source graphing and data visualisation tools and found Flot to be quite nice and its developed by some Django and jQuery fans, so maybe I am biased. Flot is a pure Javascript plotting library.

So I have a cron script that will scrape data from the RHB Bank website and writes it into a CSV file. I used BeautifulSoup to easily extract the data out of the HTML. I setup another cron script that will use the data from the CSV file and it will generate the HTML that will contain all data that is needed by Flot to draw the graph.

Flot is pretty easy to use and the basic conventions are pretty good. Since its a pure Javascript library all the code is on the HTML page and you can check it out if you want. I was thinking of adding it to Github gist but I think its not necessary at the moment since the code is very specific to my own needs. The documentation and examples are pretty good and its quite easy to learn. I particularly like the autoscaleMargin property for configuring how much margin it should automatically add to the axes so that the min and max value for the data would not be rendered on the edge of the grid. I also particularly like how easy it is to do selection and zooming. Just a few lines of code and its done.

So why did I mention I used a bit of Django?

I was lazy to find (and learn and setup) another templating language and decided to use Django's templating engine instead since the setup of that server that I am using works with Django. The HTML file that is generated is rendered off a Django template file using render_to_string() and I just pipe the stdout to a file. The only unsavoury thing is that I need to setup the DJANGO_SETTINGS_MODULE=settings and the settings.py file has only the TEMPLATE_DIRS setting.

Okay, so the next step is to add some news feed with the forex data to put more context while looking at the data. I guess that would be another weekend and another blog post then.