Tuesday, April 15, 2014

Accessing Open Data Portal (India) using APIs

EDIT: I've wrapped up this code into an R package. You can find more info about it on this blog post and here on GitHub.

As I mentioned in my previous blog post, Government of India have started an Open Data Portal for making various data public. Most of the data-sets on the portal are available for manual download. Some of the data-sets though are also available to be accessed using APIs. In this post, I'll go over how to access that data using APIs (specifically JSON API) in R.

Again, the variety of R packages available makes this a not so difficult task. I've made use of mainly these packages - XMLRCurl, RJSONIO, plyr.

The complete process can be described in following steps -
  1. Get the resource id, API key to make the API call
  2. Recursively call API until all the data is obtained
  3. Append all the data creating a single data-set.
Now, I'll describe in details each of the above steps. The resource id is the identifier for the dataset and can be found on the website (For e.g. resource-id 6176ee09-3d56-4a3b-8115-21841576b2f6 refers to dataset on the pin-code details). Another mandatory detail when making an API call is the API key. This key can be obtained by signing up on this data portal. Thus, the API URL would look something like this -

http://data.gov.in/api/datastore/resource.json?resource_id=6176ee09-3d56-4a3b-8115-21841576b2f6&api-key=<your API key>

The content of this URL can be downloaded into R by using getURL() function. Currently, there's a limit of 100 elements that can be downloaded in a single API call. This necessitates the 2nd step - making recursive API calls until all elements have been downloaded. For accomplishing this we can add one more offset parameter to the URL. The URL would now look like - 

http://data.gov.in/api/datastore/resource.json?resource_id=6176ee09-3d56-4a3b-8115-21841576b2f6&api-key=<your API key>&offset=1

Here offset signifies the number of calls. For e.g. if in each call we are downloading 100 data elements; after downloading the 1st set of 100 elements, we'd specify offset=1 to download elements 101-200.

The data thus obtained using the recursive API calls can be converted to data.frame using ldply() and each data.frame can be combined into a master data.frame using rbind().

Following GitHub Gist describes the actual R code. You can also look at my GitHub project to proper understand the directory structure used in the code.

Sunday, February 2, 2014

Know India through Visualisations - 1

I'm going to produce just a couple of charts, a teaser of sorts in this post. In the forthcoming posts I'll dig deeper.

I was amazed with the existing list of R packages to work with spatial data, without needing to get into much of the technical details. Various R packages I've used are described along with the code.

I've obtained the state level power supply position data for the November 2004 (just a random choice) from the data portal of the government of India website. The spatial data for India with state boundaries was obtained from Global Administrative Areas website.

Above plot is generated using spplot() function from sp package, below is a similar plot generated using ggplot() function from ggplot2 package. In the plot, darker shades of blue signify higher severity of electricity shortage and lighter shades signify lower severity as can be seen from the legend. The numbers in the legend are in MU i.e. Million Units (equivalent to gigawatt hour).

The advantage of using ggplot() is that I can add additional layers onto this map easily. For e.g. I can add labels of the states as can be seen below.

The R Code for this post is shown below and can also be found on this GitHub Gist

Saturday, February 1, 2014


Through this blog I intend to work on some data analysis projects, publish the results here and get feedback from other data experts. I have exposure to R, Python, MATLAB and would be using suitable one of them based on needs. My interests range from Web scraping to Data visualization to Statistical modelling.