1. A quick bookmarklet for off-campus library access

   Tue 17 December 2013

   cfarmer

   I have been doing a fair bit of research off-campus lately, and as usual, have been having trouble accessing research materials (mainly academic publications) from home. Fortunately, Hunter College provides off-campus access to all electronic resources available to Hunter students, faculty and staff via their Library proxy server. Unfortunately, it turns out to be a huge pain to use anything other than the library search facilities (like Google Scholar) through the proxy server*. In fact, when working off-campus, you actually have to preface each URL address to licensed resources with http://proxy.wexler.hunter.cuny.edu/login?url= in order ...

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2. Will it Python?

   Tue 12 February 2013

   cfarmer

   Over the past few weeks, I’ve been following a really great blog by Carl Vogel. This blog has an excellent (growing) collection of Python examples based on porting code and examples from R to Python. In general, it is useful for those “interested in the Python data analysis toolkit and its viability as an alternative to R”. Carl draws on examples from Machine Learning for Hackers by Drew Conway and John Miles White, as well as Gelman and Hill’s Data Analysis Using Regression and Multilevel/Hierarchical Models.

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3. Because its fun to map stuff…

   Fri 30 March 2012

   cfarmer

   Its been quite a while since my last post, and its Friday and I was feeling creative, so I decided to map something! I’ve been looking for an excuse to produce a nice graphic like the one Anita Graser created to represent Vienna’s green-spaces. She used Quantum GIS to produce a hexagonal grid for representing the density of Viennese trees instead of the standard heat map or kernel density map, and the results are quite nice! I’m a huge fan of QGIS, but I tend to do most of my work in R, so I decided to ...

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4. pgRouting, OpenStreetMap, and QGIS

   Thu 14 October 2010

   cfarmer

   I mentioned a few posts back that there was a great resource for downloading OpenStreetMap data, and that it was relatively easy to import osm data into PostgreSQL/PostGIS for use with pgRouting to calculate shortest paths and various other network-based operations. In this post, I’ll outline the steps required to get all this up and going, and provide a quick example to show how this can be combined with QGIS to visualise the computed shortest path directly.

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5. PostGIS ‘select’ statement as vector layer in QGIS

   Tue 27 April 2010

   cfarmer

   Several colleagues of mine have asked whether it is possible to visualise the results of a SELECT statement on a PostGIS database that returns spatial data in QGIS. In other words, can we map the results of something like:

   SELECT id, st_union(the_geom) FROM spatial_table GROUP BY id;
   

   My usual answer to this in the past has been “not yet…”, but now thanks to Giuseppe Sucameli and Jürgen E. Fischer, the answer is a resounding “yes!”. A recent patch to QGIS trunk now makes custom Postgres queries possible via the postgres data provider.

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6. Parallel bootstrapping with R

   Wed 21 April 2010

   cfarmer

   In a recent post, I mentioned that I was testing the stability of clusters generated from a modified network partitioning algorithm using bootstrap resampling techniques. I also mentioned that I was doing this in R, using the very nice foreach package published by REvolution Computing. To show just how nice this package is, below is a minimal example of bootstrapping a network partitioning algorithm which takes advantage of a multicore processor:

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7. Bootstrapping network partitioning methods

   Sat 17 April 2010

   cfarmer

   My PhD research at the moment focuses on network-based algorithms for delineating functional regions (geographical regions within which a large majority of the local population seeks employment, and the majority of local employers recruit their labour). Currently I’m using a network partitioning algorithm based on modularity maximisation. I have found my results to be quite good so far, but, ‘quite good’ isn’t really a very scientific description of validity, so obviously some others means of validation is required. Enter bootstrap resampling!

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8. QGIS developer meeting update

   Wed 11 November 2009

   cfarmer

   Last week I attended the 2009 QGIS Developers Meeting in Vienna, Austria. We all had a really good time, met many new people, and actually got a lot done in the process. There have been updates about the meeting (hackfest) on the QGIS blog, and Tim Sutton has written a few words about our progress as well. I’m not going to repeat what others have said, but I would like to give a quick update on the work that I was doing at the meeting, and show off the new geoprocessing features now available to all QGIS developers (Python and C++).

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