Data Science Is Hard : A Look At Sotchi Olympics
Data Science is hard. I'll use an example that made lots of buzz to show some of the issues with data science. Two brothers, Dan and Tim Graettinger, who work for Discovery Corps, Inc. devised a predictive model that predicts medal count per country for the Sotchi Olympics. The Graettinger brothers model was commented on most data science and analytics sites, in OR blogs (see Laura McLay's entry) , even beyond . Question is: did they predict medal count correctly?
Before answering that question let me... [More]
Tags: data_science analytics 
Solving the hardest Sudoku  part 2
My previous post on Sudoku described how a fairly simple OPL model could be used to solve a hard Sudoku problem. I ended the post this way:
What?
What do you say?
I see, you're asking about the solution to the above Sudoku. Well, why not download CPLEX for free and run the above model to find out?
This post is a detailed tutorial on how to run that Sudoku model on a Windows PC using CPLEX. It also addresses an interesting challenge about using Microsoft Excel for defining the problem data... [More]

Solving the hardest Sudoku  part 1
Do you know the hardest Sudoku problem? Do you know the best way to solve it? Before answering these questions, let me remind you of what the Sudoku puzzle is about in case you haven't read a newspaper in the last decade (adapted from wikipedia ):
The objective is to fill a 9×9 grid with digits so that the digits in each column, each row, and each of the nine 3×3 subgrids that compose the grid (also called ""blocks") are pairwise different. The puzzle setter provides a partially completed grid,... [More]
Tags: constraint_programming mathematical_optimization optimization analytics mathematics sudoku 
Tower of Hanoi at Large
Did you know that the Tower of Hanoi puzzle had real world applications? I was lucky enough to be involved with one such application . Before describing the application, let me recap briefly what the puzzle is about. I'll borrow the definition from wikipedia .
The Tower of Hanoi (also called the Tower of Brahma or Lucas' Tower , [ 1 ] and sometimes pluralised) is a mathematical game or puzzle . It consists of three rods, and a number of disks of different sizes which can slide onto any rod. The puzzle starts with the... [More]
Tags: analytics constraint_programming smarter_city optimization 
Centers of Polygons in OPL
Ryan J. O'Neil has written an interesting post on centers of polygons . Reason I'm blogging here is that he also asks an interesting question for the case where the polygon is a rectangle. Before looking at rectangles, let's define the general problem. There are several definitions of the center of polygons, and we'll use the one used by Ryan: it is the center of the largest circle contained by the polygon. It is called the Chebyshev center of the polygon.
Here is an example used by... [More]
Tags: mathematics optimization analytics mathematical_optimization 