atris/cognition

Cognition

cognition

Cognition is a data mining application which mines a specific dataset and identifies patterns in them based on multiple criteria.

It works on MovieLens dataset (http://grouplens.org/datasets/movielens/) and identifies the cheaters in the dataset i.e. users who intentionally give ratings in specific intervals to manipulate ratings of movies. i.e. to delibrately bring up or down average rating of a movie or movies.

It is built using Pl/R in PostgreSQL and PostgreSQL.

To use the project, please use the .sql file and load it into a PostgreSQL database. Use the queries present in Test Queries to run the application.

Algorithm

1. A seed value(starting movie id) is given to the system.

2. The system gets the densities of ratings for the given movie.

3. System gets the ratings with the highest and lowest densities.

4. If the difference between the density of highest or lowest density rating and mean of densities of the other four intervals is greater than a threshold, the rating may have cheaters present.

    Foreach(member of potential cheaters rating(s))
    {
    If(CheaterDetected is not empty)
    {
    Calculate probability of current member being a cheater using Naive Bayes classification.
    If(probability > threshold value)
    {
    Process for cheater detection.
    }
    else
    {
    Go to next member.
    }
   
    Get all the ratings for the current user.
    risky_intervals = 0.
    Foreach(rating in ratings of current user)
    {
    	if(density of rating > mean of other four ratings 			by a threshold value OR density of rating < average density for that rating)
    	{
    		++risky_interval
    	}
    }
    if(risky_interval > (5 – risky_interval))
    {
    	print(“Cheater”);
    }
    else
    {
    	print(“Not cheater”)
    }