Category: r (Page 15 of 20)

Newton the dog and Luis with our new copy of Doing Bayesian Data Analyses — Newton and Luis with our new copy of Doing Bayesian Data Analyses

Doing Bayesian Data Analysis now in JAGS

2012-01-04 / Luis

Around Christmas time I presented my first impressions of Kruschke’s Doing Bayesian Data Analysis. This is a very nice book but one of its drawbacks was that part of the code used BUGS, which left mac users like me stuck.

Kruschke has now made JAGS code available so I am happy clappy and looking forward to test this New Year present. In addition, there are other updates available for the programs included in the book.

Plotting earthquake data

2012-01-03 / Luis

Since 4^th September 2010 we have had over 2, 800 quakes (considering only magnitude 3+) in Christchurch. Quakes come in swarms, with one or few strong shocks, followed by numerous smaller ones and then the ocasional shock, creating an interesting data visualization problem. In our case, we have had swarms in September 2010, December 2010, February 2011, June 2011 and December 2011.

Geonet provides the basic information and there have been several attempts at displaying the full set of shocks. For example, Christchurch Quake Map uses animation, while Canterbury Quake Live uses four panels showing quakes for last 24 hours, last week, last month and since September 2010. While both alternatives are informative, it is hard to see long-term trends due to overplotting, particularly when we move beyond one week during a swarm.
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An R wish list for 2012

2011-12-26 / Luis

I expect there will be many reviews and wish lists for R this year, with many of them focusing on either running speed or dealing with large data sets. However, most issues that I would like to see tackled in R next year are not technical but, for lack of a better word, social.

Many users will first encounter R through the r-project.org website. This site is begging for a redesign, which could start getting rid of the frames (which have sucked since a long time ago). At a minimum, this would make pages much easier to bookmark.

Steak at Quantum Forest's HQ — Meaty like a ribeye steak slowly cooked at Quantum Forest's HQ in Christchurch

First impressions of Doing Bayesian Data Analysis

2011-12-22 / Luis

About a month ago I was discussing the approach that I would like to see in introductory Bayesian statistics books. In that post I mentioned a PDF copy of Doing Bayesian Data Analysis by John K. Kruschke and that I have ordered the book. Well, recently a parcel was waiting in my office with a spanking new, real paper copy of the book. A few days are not enough to provide a ‘proper’ review of the book but I would like to discuss my first impressions about the book, as they could be helpful for someone out there.

R pitfall #3: friggin’ factors

2011-12-15 / Luis

I received an email from one of my students expressing deep frustration with a seemingly simple problem. He had a factor containing names of potato lines and wanted to set some levels to NA. Using simple letters as example names he was baffled by the result of the following code:

lines <- factor(LETTERS)
lines
# [1] A B C D E F G H...
# Levels: A B C D E F G H...

linesNA <- ifelse(lines %in% c('C', 'G', 'P'), NA, lines)
linesNA
#  [1]  1  2 NA  4  5  6 NA  8...