Monthly Archives: February 2010

Speeding up R code: A case study

February 22, 2010
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On his Psychology and Statistics blog, Jeromy Anglim tells how he was analyzing some data from a skill acquisition experiment. Needing to run a custom R function across 1.3 million data points, Jeromy estimated it would take several hours for the computation to complete. So, Jeromy set out to optimise the code. First, he used the Rprof function, which...

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ggplot2 (qplot) text size

February 22, 2010
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I'm trying to learn qplot in ggplot2, and I'm having a difficult time adjusting text sizes. Well, difficult doesn't descibe it - I can't do it at all. The manual tells me I can use cex just like in plot, but it's not working...

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Time-Space Cloud with R

February 22, 2010
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Time-Space Cloud with R

Here comes another option to analyze a TimeSpace-Track with R. A lattice cloud plots every recorded trackpoint into a 3d-time-space-cube. As the data (planar point pattern) is marked with the daytime, cluster of everyday routines become visible. Here the direct comparison between a function of density and the time-space-cloud. Code example: cloud(time_hours ~ PPP_selection$x *

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Post hoc analysis for Friedman’s Test (R code)

February 22, 2010
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Post hoc analysis for Friedman’s Test  (R code)

My goal in this post is to give an overview of Friedman’s Test and then offer R code to perform post hoc analysis on Friedman’s Test results. (The R function can be downloaded from here) Preface: What is Friedman’s Test Friedman test is a non-parametric randomized block analysis of variance. Which is to say it is a non-parametric version of...

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The R type system

February 21, 2010
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The R type system

R is a weird beast. Through it's ancestor the S language, it claims a proud heritage reaching back to Bell Labs in the 1970's when S was created as an interactive wrapper around a set of statistical and numerical subroutines. As a programming language,...

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The truncated Poisson

February 21, 2010
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The truncated Poisson

A common model for counts data is the Poisson. There are cases however that we only record positive counts, ie there is a truncation of 0. This is the truncated Poisson model. To study this model we only need the total counts and the sample size. This comes from the sufficient statistic principle as the

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Visual Interpretation of Principal Coordinates (of) Neighbor Matrices (PCNM)

February 21, 2010
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Principal Coordinates (of) Neighbor Matrices (PCNM) is an interesting algorithm, developed by P. Borcard and P. Legendre at the University of Montreal, for the multi-scale analysis of spatial structure. This algorithm is typically applied to a distance matrix, computed from the coordinates where some environmental data were collected. The resulting "PCNM vectors" are commonly used to describe...

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Uh!

February 20, 2010
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Didn't know this... a data 0 2 4 7+ 25 34 12 5 It's becoming clear that I have learned R in the most unstructured way...I always do it in two stages :ashamed:

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Design of Experiments – Block Designs

February 20, 2010
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Design of Experiments – Block Designs

In many experiments where the investigator is comparing a set of treatments there is the possibility of one or more sources of variability in the experimental measurements that can be accounted for during the design stage of the experimentation. For example we might be investigating four different pieces of machinery using say two different operators,

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Does a Proclamation of Increased Workout Load Matter?

February 20, 2010
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Does a Proclamation of Increased Workout Load Matter?

I forgot to link this up, but I have a new article (joint with our editor) over at Fantasy Ball Junkie. I run an extremely crude model to see if players who were mentioned in the media as having lost weight, gained muscle, gained speed, got eye surgery...

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