## Visual Gallery

As the end of year 2016 is approaching, I decided to gather and summarize my visualizations on one page. Have a look. Visual Gallery Happy new year! Cheers! #visual #analytics #bigdata #BI #ML #datamining #mmds #plots  Post by @dzhamzic. Source: Visual Gallery

## From Recursion to Tail Recursion in Scala

#scala #recursion #optimization

## Twitter API Streaming in Python

Maybe the easiest way to connect to Twitter API and to stream tweets, is using Python and Tweepy. You can install Tweepy using pip: Tweepy is an open source library and you can check the source here. Maybe, take a peak at StreamListener class and see what additional options are available. ‘Nuff said. Here’s the ...

## Google’s PageRank Algorithm in Python

Have you ever asked yourself how google ranks the pages when you search something on google.com? If yes, have a look at PageRank algorithm definition. I’ll not go into much details here, but to give you an idea, the World Wide Web can be seen as a large graph, consisting of pages as nodes and ...

## A Star (A*) Algorithm with Caching – Java Implementation

Route calculation is computationally an expensive operation. There are several ways how to reduce computational load on the backend. I’ll show you how I optimized my computational resources. There are times where a bunch of people is heading to the same event using the same or at least similar paths. Following this logic, it is ...

## A Star (A*) Algorithm Implementation in Java

A* algorithm can be seen as an heuristic extension of Dijkstra’s. Whereas in the Dijkstra’s priority-queue ordering is based only on the distance from the start node to the current, A* algorithm additionally calculates the distance from the current node to the goal-node. Thus the ordering in the priority queue is different and the algorithm ...

## Dijkstra’s Algorithm implementation in Java

The Breadth First Search (BFS) algorithm basically checks only if there is a path from node A to node B. It’ doesn’t necessarily find the shortest path between two graph nodes. Here comes Dijkstra into the game. Dijkstra’s algorithm finds the shortest possible route between two graph nodes. The main difference between Dijkstra and BFS ...

## Breadth First Search (BFS) in Java – Code

Long time ago, I had to implement BFS in Java as a part of exercise at the university. BFS, like Depth First Search (DFS), is a search algorithm for graphs and trees. They have uses in route planing(google-maps, navigation devices etc.) and in many other applications. You can read about some use cases and DFS vs. BFS ...

## Anonymous Web Scraping with Python Selenium PhantomJS Xpath and TOR

Using pure selenium methods to extract data from metasearch websites is quite tricky and uses a lot of CPU resources. I have spent significant amount of time with selenium built-in methods with python and have a feeling that the development is quite tedious, time consuming and prone to bugs. Selenium’s WebElement objects are not flexible, ...

## Searching neighbors in Graph Data Structure by matrix multiplication

Which vertices in graph can be reached in 1, 2 or N hops? This can basically be implemented in two ways. First, if the graph is implemented as adjacency matrix, by checking connections (ones in double array or a row) and iterating further. Second, if the graph structure is implemented as ArrayList, by checking lists of ...

## Java MapReduce for top N Twitter Hashtags

Back in 2015 i had to implement MapReduce job to extract top 15 hashtags from  twitter’s raw data in Hadoop. This was a part of Business Intelligence lecture exercise at Vienna University of Technology. Regex used (not the best one by my opinion), for hashtag extraction, has following format: String regex = “text\”:\\\”(.*)\\\”,\”source”; The ‘source’ field comes ...

## Black Jack in Java

Back in 2009 at the University we had to implement a game for mobile devices in J2ME. We chose Black Jack and I did the business logic. The logic consists of 3 packages. The bl package implements interfaces from the interfaces package and the executable is in the game package. So here is the code … Package: game ...

## Linear Regression with multiple Variables in Matlab

In the previous post I showed you how to implement Linear Regression with one Variable in Matlab.  In this one I’m going to discuss implementation with multiple variables. Before implementing multivariate Linear Regression, feature normalization would be the smart step since the gradient descent would converge (would find minimum cost function) much more quickly. Every sample value is ...

## Linear Regression with one Variable in Matlab

In this post i will show you how to implement one of the basic Machine Learning concepts in Matlab, the Linear Regression with one Variable. Matlab and Octave are very useful high-level languages for prototyping Machine Learning algorithms.   [Linear Regression Example from mathworks.com] The idea is to find the line that perfectly fits all ...