JSM 2013 – Tuesday

August 7, 2013
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JSM 2013 – Tuesday

The Joint Statistical Meeting in Montreal has proven to be very good.   Here are a few highlight from Tuesday’s sessions.  There is one major problem that exists and that is there are too many good sessions to attend.  During one time block I had six session that I wanted to go to.  Unfortunately, it

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Assessing the precision of classification tree model predictions

Assessing the precision of classification tree model predictions

My last post focused on the use of the ctree procedure in the R package party to build classification tree models.  These models map each record in a dataset into one of M mutually exclusive groups, which are characterized by their average response.  For responses coded as 0 or 1, this average may be regarded as an estimate of...

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Cronbach to the future

August 6, 2013
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One fascinating thing about working in the area of psychological statistics is how hard it is to move people away from reliance on bad, inefficient or otherwise problematic methods. My own view - informed to some extent by the literature, by experience and by anecdote is that it isn't sufficient merely to establish than the standard approach is wrong....

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How to choose a new business location with R

August 6, 2013
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How to choose a new business location with R

This guest post is by Rodolfo Vanzini. Rodolfo is senior partner at eXponential.it — an asset management consultancy based in Italy — and advises clients on investment management issues. He taught at the University of Siena and is an analytics professional. With an economist education and a financial markets expertise four years ago I thought I couldn't be of...

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JSM 2013 – Monday

August 6, 2013
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JSM 2013 – Monday

I am currently attending the 2013 Joint Statistical Meeting in Montreal. I will try to share a few if the things that I take away each day. Last night (Monday) I attended the JSM keynote speaker with Nate Silver and it proved to be a very interesting discussion.  Silver is best known for his work

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The Stats Chat Blog

August 6, 2013
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Recently, I've begun following the Stats Chat blog. Run by the Department of Statistics at the University of Auckland - the largest statistics department in New Zealand or Australia (and the birthplace of R) - this blog apparently started in April of this year.It's aim is:"to foster discussion of data around us, particularly in the media, and...

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Read the source code

August 6, 2013
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Read the source code

The other day, there was a bit of a twitter conversation about qqline in R. It made me think: how exactly is the line produced by qqline chosen? I seemed to recall that the line was through the first and third quartiles. An advantage of R is that you can just type the name of

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I Want ggplot2/lattice and d3 (gridSVG–The Glue)

August 6, 2013
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I Want ggplot2/lattice and d3 (gridSVG–The Glue)

I really like interactive graphics, especially when they come straight from R.  I posted a lot about rCharts, but it is not the only way.  In my mind there are three types of glue to link R to SVG/HTML/Javascript: Let R do the data and then send the data to Javascript to create the SVG graphics....

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Tabular Data I/O in Julia

August 6, 2013
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Importing tabular data into Julia can be done in (at least) three ways: reading a delimited file into an array, reading a delimited file into a DataFrame and accessing databases using ODBC. Reading a file into an array using readdlm The most basic way to read data into Julia is through the use of the Tabular Data I/O...

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Informative leaflet on R

August 6, 2013
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Informative leaflet on R

We often meet clients who might have never heard of R or who are not really familiar with the power of that nice open-source statistical engine. Instead of explaining the advantages and potentials of using R personally at meetings, we came up with...

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Setting axes limits with googleVis

August 6, 2013
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I posted about the various googleVis axis options for base charts, such as line, bar and area charts earlier, but I somehow forgot to mention how to set the axes limits.Unfortunately, there are no arguments such as ylim and xlim. Instead, the Google Ch...

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Item Equating with same Group – SAT, ACT example

August 5, 2013
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Item Equating with same Group – SAT, ACT example

# Item equating is the practice of making the results from two # different assessments equivalent. This can be done by either# 1. having the same group take both assessments# 2. having equivalent groups take the different assessments# 3. having non-eq...

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Google Developers R Programming Video Lectures

August 5, 2013
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Google Developers recognized that most developers learn R in bits and pieces, which can leave significant knowledge gaps. To help fill these gaps, they created a series of introductory R programming videos. These videos provide a solid foundation for p...

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Explore smartphone market share with Nanocubes

August 5, 2013
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Explore smartphone market share with Nanocubes

Back in May, Twitter's Miguel Rios created some beautiful data visualizations to show that with enough (i.e. billions) of geotagged tweets, you can reveal the geography of where people live, work and commute. Now, a new interactive visualization of 210 million geotagged tweets by AT&T Research Labs reveals the market share of iPhone, Android and Windows smartphones down to...

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Classifieur Naïf Bayésien

August 5, 2013
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IntroductionLe classifieur naïf bayésien est l'une des méthodes les plus simples en apprentissage supervisé basée sur le théorème de Bayes. il est peu utilisé par les praticiens du data mining au détriment des méthodes traditionnelles que sont les arbres de décision ou les régressions logistiques.Un avantage de cette méthode est la simplicité de programmation, la facilité d'estimation des paramètres...

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Calendar-based Sector Strategy

August 5, 2013
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Calendar-based Sector Strategy

I recently came across the Kaeppel’s Sector Seasonality Strategy which is described in Kaeppel’s Corner: Sector Seasonality and updated in Kaeppel’s Corner: Get Me Back, Clarence. Today I want to show how to back-test the Kaeppel’s Sector Seasonality Strategy using the Systematic Investor Toolbox. Following are the strategy rules: Buy Fidelity Select Technology (FSPTX) at

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How Much Should Bale Cost Real?

August 5, 2013
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How Much Should Bale Cost Real?

It looks increasingly likely that Gareth Bale will transfer from Tottenham to Real Madrid for a world record transfer fee. Negotiations are ongoing, with both parties keen to get the best deal possible deal with the transfer fee. Reports speculate that this transfer fee will be anywhere in the very wide range of £80m to

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Drawing a 95% confidence interval in R

August 5, 2013
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Drawing a 95% confidence interval in R

I’m writing a post on how to draw a in 95% confidence interval in R by hand. I spent an hour or so trying to figure this out, and most message threads point someone to the ellipse() function. However, I wanted … Continue reading →

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Creating as and wrap for sparse matrices

August 5, 2013
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Creating as and wrap for sparse matrices

An earlier article discussed sparse matrix conversion but stopped short of showing how to create custom as<>() and wrap() methods or functions. This post starts to close this gap. We will again look at sparse matrices from the Matrix package for R, as well as the SpMat class from Armadillo.At least for now we will limit outselves...

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Heatmapping Washington, DC Rental Price Changes using OpenStreetMaps

August 4, 2013
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Heatmapping Washington, DC Rental Price Changes using OpenStreetMaps

Percentage change of median price per square foot from July 2012 to July 2013: Percentage change of median price from July 2012 to July 2013: Last November I made a  choropleth of median rental prices in the San Francisco Bay Area using data from my company, Kwelia.  I have wanted to figure out how to

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Changepoint Analysis of Time Series?

August 4, 2013
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Changepoint Analysis of Time Series?

Last time we downloaded data from quandl.com.  This was privately-owned homes completed in a month in thousands of units(not seasonally adjusted).  Now, let's take a look at some basic R functions to examine time series along with my first ex...

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RcppArmadillo 0.3.900.7

August 4, 2013
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A bug-fix release 3.900.7 of Armadillo was provided by Conrad a few days ago. It has been rolled into a new RcppArmadillo release 0.3.900.7 which, after a brief delay, is now on CRAN and in Debian. The main bug fix is a change in the in-place vers...

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More rainfall calculations – REML

August 4, 2013
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More rainfall calculations – REML

I wanted to have a look at various REML methods for a long time. The rainfall data seemed a nice example. On top of that, FreshBiostats had a blog post 'Mixed Models in R: lme4, nlme, or both?'. So lme4 it is.The data  As described before; th...

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A new R trick … for me at least

August 3, 2013
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What were going to be talking about today are dynamic argument lists for functions. Specifically, how to unpack and prepare them in R using ..., list(), and do.call()Biased by Matlab and varargin Initially, I based my use of ... in R on my experience w...

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Classification of the Hyper-Spectral and LiDAR Imagery using R (mostly). Part 2: Classification Approach and Spectre Profile Creation

August 3, 2013
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Classification of the Hyper-Spectral and LiDAR Imagery using R (mostly). Part 2: Classification Approach and Spectre Profile Creation

IntroductionThis is the second part of my post series related to hyper-spectral and LiDAR imagery using R. See other parts: Part 1: Result Evaluation. In this part I will describe my general approach to classification process and then I will show you how to create cool spectral response plots like this:

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Maximum Observed Windspeeds Using H*Wind Analyses

August 3, 2013
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Maximum Observed Windspeeds Using H*Wind Analyses

Building off of my last post using H*Wind data, I decided to examine the maximum windspeeds produced by Hurricane Katrina. The R code used to produce this post is available via Github. The trick here was to mung (“muhnj”) the data to produce a single plot of maximum windspeeds. There are 38 shapefiles corresponding to... Continue reading » The...

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The tenure of Doctor Who incarnations

August 3, 2013
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The tenure of Doctor Who incarnations

With a new actor being announced tomorrow, it got me pondering about the good Doctor. Specifically, who is the longest serving doctor? IMDB has the data: Let’s plot it to see how it changes over time. There was a definite shift after Tom Baker towards a shorter term as the doctor. In terms of screen

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Uncertainty in parameter estimates using multilevel models

August 3, 2013
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David Hsu writes: I have a (perhaps) simple question about uncertainty in parameter estimates using multilevel models — what is an appropriate threshold for measure parameter uncertainty in a multilevel model? The reason why I ask is that I set out to do a crossed two-way model with two varying intercepts, similar to your flight The post Uncertainty...

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Gibbs Sampler in C++

August 3, 2013
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Gibbs Sampler in C++

Markov Chain Monte Carlo (MCMC) is a popular simulation method. As it is somewhat demanding, it is also frequently used to benchmark different implementations or algorithms. One particular algorithm has been compared a number of times, starting with an article by Darren Wilkinson, and Darren’s follow–up article which in turns responded in part to our article. This post...

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