Monthly Archives: July 2009

Probability exercise: negative binomial distribution

July 19, 2009
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Probability exercise: negative binomial distribution

What is the probability you get the 4th cross before the 3rd head, flipping a coin?The mathematical formula for solving this exercise, which follows a negative binomial distribution, is:$$f(x)=P(X=x)=\begin{pmatrix} x+y-1\\ y-1 \end{pmatrix} \cdot p^x ...

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New RInside release

July 19, 2009
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I just rolled up a new release of RInside, my C++ wrapper classes which facilitate embedding R into your own C++ application. This releases owes a big Thank you! to Miguel Lechón who not only noticed errant behaviour and occassional segfaults with overly long commands sent to the embedded R, but even traced it to an oversight of mine in a simple memory buffer class...

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David Varadi’s RSI(2) alternative

July 19, 2009
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David Varadi’s RSI(2) alternative

Here's a quick R implementation of David Varadi's alternative to the RSI(2).  Michael Stokes over at the MarketSci blog has three great posts exploring this indicator: Varadi’s RSI(2) Alternative: The DV(2) RSI(2) vs. DV(2) Last Couple...

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A probability exercise on the Bernoulli distribution

July 18, 2009
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A probability exercise on the Bernoulli distribution

What is the probability, flipping a coin 8 times, to obtain the sequence HHTTTHTT? (H = head; T= tail)The theory teaches us that to solve this question, we can simply use the following formula:$$f(x)=P(X=x)=B(n,p)=\begin{pmatrix}n\\ x \end{pmatrix} \cd...

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Let us practice with some functions of R

July 18, 2009
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Let us practice with some functions of R

Given the following data set, compute the arithmetic mean, median, variance, standard deviation; find the greatest and the smaller value, the sum of all values, the square of the sum of all values, the sum of the square of all values; assigne the ranks...

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Book excerpts now posted

July 18, 2009
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Book excerpts now posted

We've posted excerpts from the book on the book website. The excerpts include Chapter 3 (regression and ANOVA) in its entirety. This demonstrates how the entries (the generic descriptions of software functions) and the worked examples reinforce each ...

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Parsing GEO SOFT files with Python and Sqlite

July 17, 2009
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Parsing GEO SOFT files with Python and Sqlite

NCBI's GEO database of gene expression data is a great resource, but its records are very open ended. This lack of rigidity was perhaps necessary to accommodate the variety of measurement technologies, but makes getting data out a little tricky. But, a...

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Simple Data Visualization

July 16, 2009
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Simple Data Visualization

OK, so, I know I already raved about one Hadley Wickham project and how it has changed my life last week. But what can I say, the man is a genius. And if you are using R (and let’s face it, you should be) and you want simple sexy graphs made quick, the man has

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Influence.ME: Simple Analysis

July 16, 2009
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Influence.ME: Simple Analysis

With the introduction of our new package for influential data influence.ME, I’m currently writing a manual for the package. This manual will address topics for both the experienced, and the inexperienced users. I will also present much of the content ...

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Missing data, logistic regression, and a predicted values plot (or two)

July 15, 2009
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miss attach miss result1 summary(result1) Call: glm(formula = a ~ b, family = binomial(logit)) Deviance Residuals: Min 1Q Median 3Q Max -1.8864 -1.2036 0.7397 0.9425 1.4385 Coefficients: ...

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