This is a gem of a book. It will become the book I give PhD students when they are learning how to write good R code. That is, if I ever see it again. I had hoped to write a review of it, but I haven’t seen it since ... [Read more...]

Books written to teach a general purpose programming language are usually organized according to the features of the language and examples often show how a particular language feature is interpreted by a compiler. Books about domain specific languages are usually organized in a way that makes sense in the corresponding ... [Read more...]

A/B testing is a method for comparing the effectiveness of several different variations of a web page. For example, an online clothing retailer that specializes in mens’ streetwear may want to examine whether a black or pink background results in more purchases from visitors to the site. Lets say ... [Read more...]

There is a nice short article on memory issue in R at http://www.matthewckeller.com/html/memory.html. If you use R to process large data, you might find it helpful. It introduces: - checking how much memory an object is taking; - the memory … Continue reading → [Read more...]

Matt Chandler vs. Mark Driscoll I came across an interesting API from Viral Heat which is capable of “Sentiment Analysis.” This analysis is designed to capture the sentiment of a statement by ranking it on a scale from -1 to 1. For instance, a chipper sentence like “The smell of roses ... [Read more...]

I couldn’t let this one go. The conclusion draw here by this author that Randy Johnson was “the best pitcher of all time” was not something I could allow to slip through the cracks. Johnson was awesome. Incredible to watch. … Continue reading → [Read more...]

My intuition tells me that objects traveling through the air would meet more resistance when there is more moisture in the air. It turns out that my intuition is wrong. It still doesn’t make sense to me but apparently humid … Continue reading → [Read more...]

I asked my research group recently what they wished they had learned before they started work on a PhD. Here are some of the responses. More mathematics. Particular topics they named included real analysis, functional analysis, measure theory, algebra, linear algebra. That would have been my response also. I still ... [Read more...]

The subset function is available in base R and can be used to return subsets of a vector, martix, or data frame which meet a particular condition. In my three years of using R, I have repeatedly used the subset() function and believe that it is the most useful tool ... [Read more...]

This post shows an example on text mining of Twitter data with R packages twitteR, tm and wordcloud. Package twitteR provides access to Twitter data, tm provides functions for text mining, and wordcloud visualizes the result with a word cloud. … Continue reading → [Read more...]

In a previous post, I discussed how to generate PPC keywords in R. In this post I will provide another example of how to perform this task. Let’s say that I am a auto insurance company that only operates in the state of Illinois. I’m planing on bidding ... [Read more...]

I came across a problem below when doing stemming and stem completion with package tm in R. Word “mining” was stemmed to “mine” with stemDocument(), and then completed to “miners”with stemCompletion(). However, I prefer to keep “mining” intact. For stemCompletion(), … Continue reading → [Read more...]

Paid search marketing refers to the process of driving traffic to a website by purchasing ads on search engines. Advertisers bid on certain keywords that users might search for, and that determines when and where their ads appear. For example, an individual who owns an auto dealership would want to ... [Read more...]

Sure thing….this is just the sort of thing for which rOpenSci is being built. A colleague of mine recently saw our packages in development and thought, “Hey, that could totally make my life easier.”   What was made easier you ask?   This was his situation: He had a list of ... [Read more...]

Despite the fact that Excel is the most widespread application for data manipulation and (perhaps) analysis, R's support for the xls and xlsx file formats has left a lot to be desired. Fortunately, the XLConnect package has been created to fill this void, and now JGR 1.7-8 includes integration with ... [Read more...]

Everyday, a poor soul tries to understand copulas by reading the corresponding Wikipedia page, and gives up in despair. The incomprehensible mess that one finds there gives the impression that copulas are about as accessible as tensor theory, which is a shame, because they are actually a very nice tool. ... [Read more...]

An R Cookbook can be found at http://code.ca-net.org/R%20Cookbook. It is a short web document presenting dozens of examples on - Accessing Database with packages RSQLite, RMySQL, RdbiPgSQL and RODBC; - Reading and Writing Data; - Date/Time variable; - Graphics; - … Continue reading → [Read more...]

  This is the first in a series of blog posts in which I use the R package GGPlot2 to examine real world data. In this post, I construct a line graph of U.S. shoe consumption from 1995 to 2007. A recent survey conducted by Shop Smart magazine found that the average ... [Read more...]

Below is a chart of the top 20 offensive players based on FanGraphs WAR for the 2011 season.  The various features and their corresponding metric are clear in the image. I’ve also included the leader and last place for each … Continue reading → [Read more...]

Last week a question came up on Stack Overflow about determining whether a variable is distributed normally. Some of the answers reminded me of a common and pervasive misconception about how to apply tests against normality. I felt the topic was general enough to reproduce my comments here (with minor ... [Read more...]