Third Milano R net meeting to be held on April 18, 2013

March 12, 2013
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Third Milano R net meeting April 18, 2013 @ 6.00 PM Fiori Oscuri Bistrot & Bar Via Fiori Oscuri, 3 Milano Further details will be published shortly. Stay connected!

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How to use optim in R

March 12, 2013
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How to use optim in R

A friend of mine asked me the other day how she could use the function optim in R to fit data. Of course there are functions for fitting data in R and I wrote about this earlier. However, she wanted to understand how to do this from scratch using optim. The function optim provides algorithms for general...

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Generating a multivariate gaussian distribution using RcppArmadillo

March 12, 2013
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Generating a multivariate gaussian distribution using RcppArmadillo

There are many ways to simulate a multivariate gaussian distribution assuming that you can simulate from independent univariate normal distributions. One of the most popular method is based on the Cholesky decomposition. Let’s see how Rcpp and Armadillo perform on this task. #include <RcppArmadillo.h> // ] using namespace Rcpp; // ] arma::mat mvrnormArma(int n, arma::vec mu, arma::mat sigma) { int ncols...

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Generating a multivariate gaussian distribution using RcppArmadillo

March 12, 2013
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Generating a multivariate gaussian distribution using RcppArmadillo

There are many ways to simulate a multivariate gaussian distribution assuming that you can simulate from independent univariate normal distributions. One of the most popular method is based on the Cholesky decomposition. Let’s see how Rcpp and Armadillo perform on this task. #include <RcppArmadillo.h> // ] using namespace Rcpp; // ] arma::mat mvrnormArma(int n, arma::vec mu, arma::mat sigma) { int ncols...

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High Resolution Figures in R

March 12, 2013
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High Resolution Figures in R

As I was recently preparing a manuscript for PLOS ONE, I realized the default resolution of R and RStudio images are insufficient for publication. PLOS ONE requires 300 ppi images in TIFF or EPS (encapsulated postscript) format. In R plots … Continue reading →

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R 101

March 11, 2013
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as.character() is your friendas.character() is your friend Sometimes when you open a data file (lets say a .csv), variables will be recognized as factor whereas it should be numeric. It is therefore tempting to simply convert the variable to numeric using as.numeric(). Big mistake! If...

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Simulating Random Multivariate Correlated Data (Categorical Variables)

March 11, 2013
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Simulating Random Multivariate Correlated Data (Categorical Variables)

This is a repost of the second part of an example that I posted last year but at the time I only had the PDF document (written in ). This is the second example to generate multivariate random associated data. This example shows how to generate ordinal, categorical, data. It is a little more complex than generating continuous

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Interview with Boulder BI Brain Trust

March 11, 2013
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On Friday I traveled to Boulder, CO to update the Boulder BI Brain Trust on the latest news and updates from Revolution R Enterprise. While I was there, I was interviewed by BBBT president Claudia Imhoff. In a wide-ranging chat, we discussed: What's behind the Revolution Analytics momentum over the past year? How Business Intelligence relates to Data Science...

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Simulating Allele Counts in a population using R

March 11, 2013
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Simulating Allele Counts in a population using R

This post is inspired by the Week 7 lectures of the Coursera course "Introduction to Genetics and Evolution" (I highly recommend this course for anyone interested in genetics, BTW.) Professor Noor uses a Univ Washington software called AlleleA1 for try...

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Reproducible Research at ENAR

March 11, 2013
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I gave a talk at the Spring ENAR meetings this morning on some of the technical aspects of creating the book. The session was on reproducible research and the slides are here. I was dinged for not using git for version control (we used dropbox for simp...

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Lipsyncing for your life: a survival analysis of RuPaul’s Drag Race

March 11, 2013
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Lipsyncing for your life: a survival analysis of RuPaul’s Drag Race

If you follow me on Twitter, you know that I’m a big fan of RuPaul’s Drag Race. The transformation, the glamour, the sheer eleganza extravanga is something my life needs to interrupt the monotony of grad school. I was able to catch up on nearly four seasons in a little less than a month, and I’ve been watching the… Continue reading →

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Veterinary Epidemiologic Research: Linear Regression Part 3 – Box-Cox and Matrix Representation

March 11, 2013
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Veterinary Epidemiologic Research: Linear Regression Part 3 – Box-Cox and Matrix Representation

In the previous post, I forgot to show an example of Box-Cox transformation when there’s a lack of normality. The Box-Cox procedure computes values of which best “normalises” the errors. value Transformed value of Y 2 1 0.5 0 -0.5 -1 -2 For example: The plot indicates a log transformation. Matrix Representation We can use

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Simulating Random Multivariate Correlated Data (Continuous Variables)

March 11, 2013
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Simulating Random Multivariate Correlated Data (Continuous Variables)

This is a repost of an example that I posted last year but at the time I only had the PDF document (written in ).  I’m reposting it directly into WordPress and I’m including the graphs. From time-to-time a researcher needs to develop a script or an application to collect and analyze data. They may also need

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Hexadecimal literals in GNU R

March 11, 2013
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Recently I have used hexadecimal numbers in GNU R. The way they are parsed surprised me and is inconsistent with Java. As R Language Definition pdf only briefly mentions hexadecimal numbers here is what I have found.First I have checked the following c...

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FBit: GitHub repo for posts with R code for this blog

March 11, 2013
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FBit: GitHub repo for posts with R code for this blog

This is a test post since I want to improve upon Jeffrey Horner’s strategy for posting R code in Tumblr. The only minor improvement I wanted to try out is hosting the images directly on the web. I mean, right now the images won’t show in RSS readers. I’m not doing anything new at all, just using the...

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Discovering Argon with the 2-Sample t-Test

Discovering Argon with the 2-Sample t-Test

I learned about Lord Rayleigh’s discovery of argon in my 2nd-year analytical chemistry class while reading “Quantitative Chemical Analysis” by Daniel Harris.  (William Ramsay was also responsible for this discovery.)  This is one of my favourite stories in chemistry; it illustrates how diligence in measurement can lead to an elegant and surprising discovery.  I find

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Is CTA trend following Dead?

March 10, 2013
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Is CTA trend following Dead?

                                         This i...

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More sequential testing for triangle tests

March 10, 2013
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More sequential testing for triangle tests

I looked before at triangle tests and at sequential testing in triangle tests (blog entry). In the latter post it was demonstrated that a sequential test is possible, without costs in desired error of the first kind. The latter because t...

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Analyse Quandl data with R – even from the cloud

March 10, 2013
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Analyse Quandl data with R – even from the cloud

I have read two thrilling news about the really promising time-series data provider called Quandl recently: Quandl: A Wikipedia for Time Series DataQuandl package released to CRANWith the help of the Quandl R package* (development version...

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Better logging in R (aka futile.logger 1.3.0 released)

March 10, 2013
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Better logging in R (aka futile.logger 1.3.0 released)

In many languages logging is now part of the batteries included with a language. This isn’t yet the case in …Continue reading »

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Call for participation: DMApps 2013 – an International Workshop on Data Mining Applications in Industry and Government

March 10, 2013
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Call for participation: DMApps 2013 – an International Workshop on Data Mining Applications in Industry and Government

Call for participation: DMApps 2013 – an International Workshop on Data Mining Applications in Industry and Government in conjunction with PAKDD 2013, Gold Coast, Australia, April 14, 2013 http://dmapps2013.rdatamining.com To attend the workshop, you need to register for PAKDD 2013 … Continue reading →

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Notes on my R / Git workflow

March 10, 2013
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These are some notes on my current R git work flow, which is quite fluid, and git has enough quirks that I usually forget part of it ! Creating Projects I've used both RStudio and Eclipse.  RStudio seems easier to create a 'project' and add a loca...

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Calculating Custom Fantasy Football Projections for Your League using R

March 9, 2013
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Calculating Custom Fantasy Football Projections for Your League using R

In prior posts, I have shown how to download fantasy football projections from ESPN, CBS, and NFL.com.  In this post, I will demonstrate how to take the projected points from these sources and The post Calculating Custom Fantasy Football Projections for Your League using R appeared first on Fantasy Football Analytics.

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Calculating Custom Fantasy Football Projections for Your League using R

March 9, 2013
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Calculating Custom Fantasy Football Projections for Your League using R

In prior posts, I have shown how to download fantasy football projections from ESPN, CBS, and NFL.com.  In this post, I will demonstrate how to take the projected points from these sources and calculate the projected points for your custom league ...

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Getting flexible with SAP HANA

Getting flexible with SAP HANA

Most of you might not be aware of a feature introduced on SAP HANA SPS5. This new feature is called "Flexible Tables", which means that you can define a table that will grow depending on your needs. Let's see an example...You define a table with ID, NA...

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MCMSki IV, Jan. 6-8, 2014, Chamonix (news #4)

March 9, 2013
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MCMSki IV, Jan. 6-8, 2014, Chamonix (news #4)

More news about MCMSki IV! Remember, the call is still open for contributed sessions for a few more weeks, till March. 20 to be precise (make sure to contact me at [email protected] if you are considering putting one session together). To all those who already submitted a session, thanks a lot, please stay tuned, and

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Analyzing Monthly Expenses with a Pareto Chart

March 9, 2013
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Analyzing Monthly Expenses with a Pareto Chart

This month, ASQ CEO Paul Borawski encourages us to share stories about “quality solutions in unexpected places.” This is such a fun question, because now I’ll be noticing these unexpected gems all

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Downloading NFL.com Fantasy Football Projections using R

March 9, 2013
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Downloading NFL.com Fantasy Football Projections using R

In this post, I will show how to download NFL.com fantasy football projections using R.The R ScriptThe R Script for downloading fantasy football projections from NFL.com is located at: https://github.com/dadrivr/FantasyFootballAnalyticsR...

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The Gambling Machine Puzzle

March 9, 2013
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The Gambling Machine Puzzle

This puzzle came up in the New York Times Number Play blog. It goes like this: An entrepreneur has devised a gambling machine that chooses two independent random variables x and y that are uniformly and independently distributed between 0 and 100. He plans to tell any customer the value of x and to ask him

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