Monthly Archives: September 2012

Big data analysis, for free, in R (or “How I learned to load, manipulate, and save data using the ff package”)

September 11, 2012
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Big data analysis, for free, in R (or “How I learned to load, manipulate, and save data using the ff package”)

Before choosing to support the purchase of Statistica at my workplace, I came across the ff package as an option for working with really big datasets (with special attention paid to ff dataframes, or ffdf). It looked like a good … Continue reading →

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Second Milano R net meeting

September 11, 2012
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Second Milano R net meeting

September 27, 2012 - 18:00 - 21:00 Fiori Oscuri Bistrot & Bar (www.fiorioscuri.it) Via Fiori Oscuri, 3 - Milano (Zona Brera) Continue reading →

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Connecting data to the real world – The next sexy job?

September 11, 2012
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Connecting data to the real world – The next sexy job?

At last week's Royal Statistical Society (RSS) conference Hal Varian, Chief Economist at Google, gave a panel talk about 'Statistics at Google'. Could he get a better audience than the RSS? Hal talked about his career in academia and at Google. He remi...

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Unit root, or not ? is it a big deal ?

September 10, 2012
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Unit root, or not ? is it a big deal ?

Consider a time series, generated using set.seed(1) E=rnorm(240) X=rep(NA,240) rho=0.8 X=0 for(t in 2:240){X=rho*X+E} The idea is to assume that an autoregressive model can be considered, but we don't know the value of the parameter. ...

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Extending Gold time series

September 10, 2012
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Extending Gold time series

While back-testing trading strategies I want all assets to have long history. Unfortunately, sometimes there is no tradeable stock or ETF with sufficient history. For example, I might use GLD as a proxy for Gold allocation, but GLD is only began trading in November of 2004. We can extend the GLD’s historical returns with its

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PDF and CDF for normal distributions with R

September 10, 2012
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PDF and CDF for normal distributions with R

Below, we give the R code to plot the PDF and the CDF for normal distributions. We wish to get charts quite similar to the ones read on Wikipedia (Normal Distribution). The resulting charts are shown at the bottom. Notice that … Continue reading →

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igraph 0.6 issues: Changed numbering of Vertices

September 10, 2012
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I have tried one of my previous scripts with an updated igraph version and I got an interesting (pretty much unexpected) error:At type_indexededgelist.c:269 : invalid (odd) length of edges vector, Invalid edge vectorThe problem is that it was a well-te...

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R-bloggers submission

September 10, 2012
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I might be the 393rd blogger on the R-bloggers.com :-)  http://www.r-bloggers.com/Wohoo!

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Item Response Theory: Developing Your Intuition

September 10, 2012
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Item Response Theory: Developing Your Intuition

Suppose that you accepted my argument from the last two posts on halo effects and bifactor models.  As you might recall, I argued that when respondents complete rating scales, they predominating rely on their generalized impression with a more minor role played by the specific features that the ratings were written to measure.  Consequently, we...

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Example 10.1: Read a file byte by byte

September 10, 2012
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Example 10.1: Read a file byte by byte

More and more makers of electronic devices use standard storage media to record data. Sometimes this is central to the device's function, as in a camera, so that the data must be easy to recover. Other times, it's effectively incidental, and the device maker may not provide easy access to the stored data....

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