# Monthly Archives: April 2012

## Complex arithmetic and airplane wings

April 23, 2012
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$Complex arithmetic and airplane wings$

I was once told that the reason that such a shape was so commonly used for aeroplane wings was merely that then one could study it mathemtically by just employing the Zhoukowski transformation. I hope that this is not true! (R. Penrose, “The Road to Reality”, p.150) Penrose here talks about a complex holomorphic mapping

## Drawdown Look at Frontier of Assets and Systems

April 23, 2012
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In Efficient Frontier of Funds and Allocation Systems, I had hoped to start exploring how a frontier can potentially be created with only one asset, or how an even more efficient frontier could be created with assets and also systems on those assets.&n...

## Short R script to plot effect sizes (Cohen’s d) and shade overlapping area

April 23, 2012
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In this short post I take a look at how to use R and ggplot2 to visualize effect sizes (Cohen’s d) and how to shade the overlapping area of two distributions.

April 23, 2012
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A few days ago, Andrew Barr had a great post on his blog. It was titled, "R is not just for nerds....it has drop-down menus!" You can bet that this one caught my eye when it was re-posted on R-Bloggers.Briefly, Andrew takes us through the installation and basic use of the Java Gui for R (JGR) in...

## Introduction to Oracle R Connector for Hadoop

April 23, 2012
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MapReduce, the heart of Hadoop, is a programming framework that enables massive scalability across servers using data stored in the Hadoop Distributed File System (HDFS). The Oracle R Connector for Hadoop (ORCH) provides access to a Hadoop cluster from R, enabling manipulation of HDFS-resident data and the execution of MapReduce jobs. Conceptutally, MapReduce is similar...

## Talk on quantiles at the R Montreal group

April 23, 2012
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This afternoon, I will be giving a two-hour talk at McGill on quantiles, quantile regressions, confidence regions, bagplots and outliers. Before defining (properly) quantile regressions, we will mention regression on (local) quantiles, as on the gr...

## Puzzle: A path through pairs making squares

April 23, 2012
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Ted Harding posed an interesting puzzle challenge on the r-help mailing list recently. Here's the puzzle: Take the numbers 1, 2, 3, etc. up to 17. Can you write out all seventeen numbers in a line so that every pair of numbers that are next to each other, adds up to give a square number? You can figure out...

## Tuning GAMBoost

April 23, 2012
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This post describes some of the simulation results which I obtained with the GAMBoost package. The aim of these simulations is to get a feel what I should tune and what I should not tune with GAMBoost. SetupIn the GAMBoost package one can tune qui...

## Example 9.28: creating datasets from tables

April 23, 2012
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RThere are often times when it is useful to create an individual level dataset from aggregated data (such as a table). While this can be done using the expand.table() function within the epitools package, it is also straightforward to do directly within R.Imagine that instead of the individual level data, we had only the 2x2 table for the...