Sorry for the delay between my posts. I was stuck in getting the octave modules to run on the server.  A couple of bugs held me back for the past 1-2 weeks.

1. Found some bugs in the kmeans module of octave. The processing of the optional parameters was not working if one of those parameters was missing. Also, the parameter 'start' now takes user defined initial seeding for the clustering. Wrong usage of 'lower' and 'tolower' functions in the file. Note that Octave is running slowly on the system, so debugging it is also becoming tedious (~5m per simulation). Other options like Matlab will also have to be looked into, to compare performance in real-time.

2. The issue of permissions/paths to generate the required files in the /var/www/data directory and process them using octave programatically.

3. The app was earlier tested on an older version of android. I ran it on Galaxy S2 this week and found that network operations like multipart-upload cannot be done on the main thread. So moved that part of the code to AsyncTask. Now the app is running smoothly with less crashes.

Now, the server code is running without any error, but is taking a long time to finish clustering (~10-15 min per data folder). 
Internet was down yesterday in my place. So, could not work on the server part. Updated the phone app to take comments and ratings as input. These will be sent to the server along with the other sensors' data when the user has opted to stop logging the information.