How many observations should you have before constructing a confidence interval?

A friend just e-mailed me about a blog post by Dr. AnnMaria De Mars titled “The Next Big Thing”. In it Dr. De Mars wrote (I allowed myself to emphasize some parts of the text): Contrary to what some people seem to think, R is definitely not the next big thing, either. I am always surprised when people ask me why I think...

I have been meaning to look at adding some parallel processing to R as I have some scripts that are painfully slow and embarrassingly parallel. There seem to be a lot of packages around for doing parallel computing, listed here.I decided to look at mul...

I have been meaning to look at adding some parallel processing to R as I have some scripts that are painfully slow and embarrassingly parallel. There seem to be a lot of packages around for doing parallel computing, listed here.I decided to look at mul...

William asks: How can I make a graph that looks like this, “tweet density” style, showing time intervals? He then helpfully describes his input data: a CSV file with headers “time started, time finished, date”. Here’s a simple CSV file, tasks.csv: task,date,start,end task1,2010-03-05,09:00:00,13:00:00 task2,2010-03-06,10:00:00,15:00:00 task3,2010-03-06,11:00:00,18:00:00 task4,2010-03-07,08:00:00,11:00:00 task5,2010-03-08,14:00:00,17:00:00 task6,2010-03-09,12:00:00,16:00:00 task7,2010-03-10,14:00:00,19:00:00 task8,2010-03-11,09:30:00,13:30:00 Read into R, calculate the

In case you missed them, here are some articles from last month of particular interest to R users. We reviewed a special report in The Economist on the "Data Deluge" and the growing importance of statistical analysis in business. One section mentioned R specifically. We announced that Zack Urlocker, formerly responsible for engineering and marketing for the open-source database...

I recently did an analysis for the eMERGE network where I had lots of individuals from a small town in central Wisconsin where many of the subjects were related to one another. The subjects could not be treated as independent, but I could not use a fam...

Repeated measures ANOVA is a common task for the data analyst. There are (at least) two ways of performing “repeated measures ANOVA” using R but none is really trivial, and each way has it’s own complication/pitfalls (explanation/solution to which I was usually able to find through searching in the R-help mailing list). So for future reference, I am starting this page...

In a prior article, I tried to visualize the linear global temperatures trends for a grid of start and end years. The visual I created was confusing in that the specification of color scale was interdependent with the data values. I wanted a blue -> white -> red scale of the temperatures indicating cool ->

Setting up Eclipse to use MKL-Linked RIn my previous post, I showed how to compile R 2.10.1 using Intel's Math Kernel Library for the BLAS/LAPACK interface. Even though it takes a bit of time to setup, I think the noticeably improved calculation speed justifies the effort. Although I'm happy to use R from the command line for basic stuff,...

Good news. Jeroen Ooms released a new version of his (amazing) online ggplot2 web interface: yeroon.net/ggplot2 is a web interface for Hadley Wickham’s R package ggplot2. It is used as a tool for rapid prototyping, exploratory graphical analysis and education of statistics and R. The interface is written completely in javascript, therefore there is no need to install anything on the...

Version 1.0.5 is now on CRAN. This version brings some bug fixes as well as two new features: Unlabeled code chunks are now allowed. The correct version of PGF is now checked for on startup. If the version is < 2.00, the package will fail to load....

A court in Arizona has ruled that statistical sampling is legal for determining damages awarded to individual claimants when there are thousands of similar cases to be assessed simultaneously. In a case where 30,000 claims were filed Maricopa County, AZ by hospitals for improper reimbursement, the trial judge appointed a former judge as a special master in the case...

The Trellis graphics approach provides facilities for creating effective graphs with a consistent look and feel and one of the good things about the system is the use of themes to define the colour, size and other features of the components that make up a graph. The lattice package in R is an implementation of

This is not really news. A few months ago, news broke that Facebook recorded each user’s clicks and profile views in a database. Of course, I am not at all surprised. I would be more surprised if they didn’t store every single click. By now, most people have some sense as to how Facebook’s recommendation system works. It typically performs...

Whenever you take a 1 column slice of a matrix, that gets automatically converted into a vector. But if you take a slice of several columns, it remains a matrix. The problem is you don’t always know in advance how big the slice will be, so if you do this: newMatrix

There is a central notion in Time Series Econometrics, cointegration. Loosely it refers to finding the long run equilibrium of two non-stationary series. As the most know non-stationary series examples comes from finance, cointegration is nowadays a tool for traders (not a common one though!). They use it as the theory behind pairs trading (aka

The histogram is a standard type of graphic used to summarise univariate data where the range of values in the data set is divided into regions and a bar (usually vertical) is plotted in each of these regions with height proportional to the frequency of observations in that region. In some cases the proportion of

The rationale for compiling R using the Intel Math Kernel LibraryRecently, there has been a surge in the use of Intel's Math Kernel Library (MKL; http://software.intel.com/en-us/intel-mkl/) among data analysis packages. MKL is a highly optimized set of...

The rationale for compiling R using the Intel Math Kernel LibraryRecently, there has been a surge in the use of Intel's Math Kernel Library (MKL; http://software.intel.com/en-us/intel-mkl/) among data analysis packages. MKL is a highly optimized set of...

I was recently introduced to the concept of the h-index and was compelled to find out my own h-index via Scopus. Numbers don't matter, but discussion with my colleagues turned to the issue of author position. We quickly decided that there are three important "positions" in the list of authors for a publication: first, last and everywhere else...

Posted for no other reason than it warms my gamer-geek heart to see NYC taken over by 8-bit video game characters. The Tetris sequence is particularly cool. Update: The original video was deleted from YouTube, I'm guessing because of copyright issues with the music. This version has no music. (Thanks to reader MB in the comments for the heads-up.)

REvolution R Community, REvolution's free distribution based on R from the R Project, has been updated to version 3.2 and is now available for download for Windows and MacOS. Some features of this release include: Upgraded R engine. This release is based on R 2.10.1, the latest release (as of this writing). This brings many new features to the...