Blog Archives

How many tanks? MC testing the GTP

May 25, 2010
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How many tanks? MC testing the GTP

It’s 1943 and you work for the good guys. A handful of German tanks have been captured, and each one has a serial number. This is back when serial numbers were still presumed to come in serial, one right after the other. Given your collection of numbered tanks, and assuming that any existing tank was

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R: A random walk though OOP land.

May 20, 2010
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If you are used to object oriented programing in a different language, the way R does things can seem a little strange and backwards. “proto” to the rescue. With this library you can simulate “normal” OOP. I found the examples for proto not so helpful, so to figure out how the package works I sent

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R: Dueling normals

May 18, 2010
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R: Dueling normals

More playing around with R. To create the graph above, I sampled 100 times from two different normal distributions, then plotted the ratio of times that the first distribution beat the second one on the y-axis. The second distribution always had a mean of 0, the mean of first distribution went from 0 to 4,

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Connecting R and Python

May 7, 2010
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There are a few ways to do this, but the only one that worked for me was to use Rserve and rconnect. In R, do this: 1 2 3 install.packages("Rserve") library(Rserve) Rserve(debug = FALSE, port=6311, args=NULL) Then you can connect in Python very easily. Here is a test in Python: 1 2 rcmd = pyRserve.rconnect(host='localhost', port=6311) print(rcmd('rnorm(100)'))

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R: choose file dialog box

May 6, 2010
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Needed this one recently, it pops up a window to pick a file to be used by r, then reads the contents into myData: myFile

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Game of Life in R

May 5, 2010
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Game of Life in R

Before I decided to learn R in a serious way, I thought about learning Flash/Actionscript instead. Most of my work involves evolutionary models that take place over time. I need visual representations of change. It’s certainly possible to represent change and tell an evolving story with a single plot (see for example Tufte’s favorite infographic),

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R: directing output to file on the fly, output flushing

May 4, 2010
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To start sending all output to a file, do this: sink("path/to/filename") # Direct all output to file print("Hi there") # Will be printed to file sink() # Turn off buffing to file Related to this I recently had to use: flush.console() This forces your console to print out any buffered content. Doing this will cost time, but if you are running

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First annual R plot replication prize

May 3, 2010
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First annual R plot replication prize

$100 to the first person who can figure out how I created this plot and replicate it. Some hints: It was done in R. There is only one underlying probability distribution involved (one “rdist()“). Including the “plot” statement, I created this with 3 short lines of code. This is based on a random sampling of unstated size, so

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How many girls, how many boys?

April 30, 2010
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How many girls, how many boys?

I found this interesting question over here at mathoverflow.net. Here’s the question: If you have a country where every family will continue to have children until they get a boy, then they will stop. What is the proportion of boys to girls in the country. First off, there are some assumptions you need to make that aren’t

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R: more plotting fun, this time with the Poisson

April 21, 2010
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R: more plotting fun, this time with the Poisson

Click on image for a larger version. Here is the code: par(bg="black") par(mar=c(0,0,0,0)) plot(sort(rpois(10000,100))/rpois(10000,100),frame.plot=F,pch=20,col="blue")

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