Blog Archives

Analyzing the 2011-2012 California Health Inteview Survey with R

June 1, 2014
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Analyzing the 2011-2012 California Health Inteview Survey with R

The California Health Interview Survey (CHIS) is a remarkable biannual survey of health status, care access, and demographics for California residents. The 2011-2012 public use survey data has recently been released and is freely available after registering at the CHIS site. CHIS currently offers data in SAS, Stata, and SPSS formats. However, thanks to a...

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The Circus Tent Problem with R’s Quadprog

April 20, 2014
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The Circus Tent Problem with R’s Quadprog

The MathWorks has an interesting demo on how the shape of a circus tent can be modeled as the solution of a quadratic program in MATLAB. In this post, we'll show how to solve this same problem in R using the quadprog package and also provide the technical details not covered in the Mathwork's example. In...

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Going viral with R’s igraph package

March 23, 2014
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Going viral with R’s igraph package

R's igraph package provides a simple and flexible set of utilities for working with graphs.  In this post, we'll use this package to animate the simulated spread of a disease through a network. Graphs A graph is just a collection of nodes joined by edges: require(igraph)# Specify an undirected graph by hand, using...

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Solving Quadratic Progams with R’s quadprog package

January 13, 2014
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Solving Quadratic Progams with R’s quadprog package

In this post, we'll explore a special type of nonlinear constrained optimization problems called quadratic programs. Quadratic programs appear in many practical applications, including portfolio optimization and in solving support vector machine (SVM) classification problems. There are several packages available to solve quadratic programs in R. Here, we'll work with the quadprog package. Before we dive...

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Generating Ticker Symbols with Markov Chains

November 25, 2013
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Generating Ticker Symbols with Markov Chains

Stock ticker symbols are short character string codes (AAPL for Apple, WMT for Walmart) that uniquely identify stock listings. They originate from the days when stock quotes were transmitted via telegraph. These symbols are often used as tools for branding and companies choose them to be memorable and easily recognized. As a fun and simple...

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