Original Code# One of the basic tasks in item response theory is estimating the ability of a test taker from the responses to a series of items (questions).# Let's draw the same pool of items that we have used on several previous posts:# First let's im...
POSIXct is the signed number of seconds since “the epoch”. For example it was
when I wrote this. (1351298112 UTC = Sat Oct 27, 2:35 am GMT = Fri Oct 26, 8:35 pm EST = Fri Oct 26, 5:35 pm PST = 2:35 pm HST)
POSIXlt is one of many text | character | string formats such as:
In this third part of the data types series, I'll go an important class that I skipped over so far: factors.Factors are categorical variables that are super useful in summary statistics, plots, and regressions. They basically act like dummy variables t...
A quick heads-up that I'll be presenting another brand-new webinar on Thursday next week (November 29). In Real-time Big Data Analytics: From Deployment to Production, I'll review the process of making predictive models work in real-live operational environments. I'll also tackle those ubiquitous buzz-words "real-time" and "big data", and the fact that they can mean very different things in...
At a meeting last night with some collaborators at the Vélobstacles project, I was excitedly told about the magic of IPython and it’s notebook functionality for reproducible research. This sounds familiar, I thought to myself. Using a literate programming approach to integrate computation with the communication of methodology and results has been at the core 
I’ll be subbing today for Chris, as we continue to explore some ggplot2 basics. Today, imagine that you have data distributed in two dimensions, and that you would like to convey differences in point density over space. As with many things, this...
A nice package can be both beautiful and functional. The image is CC by MIAD Communication Design.
Inspired by Read more »
We all know that the odds of flipping an unbiased coin is 50% heads, 50% tails. But what happens if you do this a lot of times. Do you expect the same number of heads and tails? What if we took a cumulative sum where heads = +1 and tails = -1. What wou...
We all know that the odds of flipping an unbiased coin is 50% heads, 50% tails. But what happens if you do this a lot of times. Do you expect the same number of heads and tails? What if we took a cumulative sum where heads = +1 and tails = -1. What wou...
This post shares the video from a talk presented on 20th November 2012 by Professor Rob Hyndman at Melbourne R Users. The talk provides an introduction to: Getting R help Debugging R functions R style guides Making good use of … Continue reading →
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).
