Thursday, March 26, 2015

Sunday, March 15, 2015

The geotemporal demographics of Twitter

This is a nice figure comparing the population pyramid of London residents and Twitter users in London. The figure comes from a new publication by Paul Longley and colleagues (UCL). Interesting how one chart can tell so much about one of the traps that come with Big Data, such as gender and age bias. Check Tim Harford's talk on the Big Data Trap.
Read more info about the paper below.


[image credit: Longley et al, 2015]


Longley P A, Adnan M, Lansley G, 2015, "The geotemporal demographics of Twitter usage" Environment and Planning A 47(2) 465 – 484.

Presentation, ungated version of the paper

Abstract:
This paper presents a preliminary empirical evaluation of the strategic importance of infusing Twitter social media data into classifications of small areas, as a way of moving beyond the nighttime residential geographies of conventional geodemographic classifications. We attempt an empirically based critique of the merits and drawbacks of the use of social media data, in which the value of high spatial and temporal granularity of revealed activity patterns is contrasted with the paucity of individual attribute information. We apply new and novel methods to enrich the profiles of Twitter users in order to generalize about activity patterns in London, our case-study city. More insidious problems in the use of social media data arise from the as-yet-unknown sources and operation of bias in their user bases. Our contribution is to begin to identify and assess the biases inherent in social media usage in social research, and use these to evaluate their deployment in research applications.

Tuesday, March 10, 2015

Message of the Day


Apparently, you've been lied to all along.

[I got this from Ray William Johnson on Facebook]

Sunday, March 8, 2015

The Queen Of Code [replay]

Celebrate women in science!

I have never heard about Grace Hopper until recently. After watching this short documentary from FiveThirtyEight, I can't believe it took me so long to know her story.

Grace Hopper was a computing pioneer in a male-dominated field. She has also invented the world's first compiler. In my lay terms Compilers are what enables computers to understand humans when we code in programming languages (e.g. Python, R, Java, etc). This is something we may take for granted today, but she is the person who conceived this idea, which made possible the rapid spread of personal computers.

This documentary is an important piece of the history of computing and a truly inspirational story, specially for women interested in coding and computer science. #InternationalWomensDay





Related Link: Gender differences in each programming language 





ps. Grace has also been credited to have coined the term "computer bug" after finding a moth stuck inside Harvard's Mark II computer in 1947, hence the term "debug" for solving problems in computer code.










Grace Hopper in 1952 (image credit: Boing Boing)

Wednesday, March 4, 2015

Mapping the Transit System of Rio with GTFS data

Here is my first experience mapping a transit system using GTFS data!

The map shows the bus public transport system of the city of Rio de Janeiro as of November 2014. The blue lines represent the bus routes, where color intensity and width vary according to service frequency per day. I have also included the city's street grid in the background (gray) to give a visual idea of the transport system coverage.

click on the image to enlarge it


The map was created in R (ggplot) using data from OpenStreetMap (OSM) and GTFS data provided by Fetranspor/Va de onibus (this is basically the same transit data people have access to in their mobile apps). This great map by James Cheshire was the main inspiration, although I couldn't get to such a nice result as James did.

I've created this map a couple of months ago but still need to organize the R code before sharing it here with you. I am also working on an interactive version of this map, but this may take a little longer  I've been facing some deadline issues lately  Stay tuned.


Related Links

Monday, March 2, 2015

Air pollution in Asian Cities

China is internationally famous for its bad air quality. So I was quite surprised to know that India has even higher levels of air pollution in many cities.


ps.  Angel Hsu has pointed out to this interactive map showing the air pollution levels in some Chinese cities in 2014. Data comes from the Ministry of Environmental Protection and you can download it here.


Sunday, March 1, 2015

Visualizing Time

Andy Kirk (who runs this great website) has organized an amazing collection of beautiful and insightful data visualizations of time. Check it out.


Soundtrack: