Monthly Archives: October 2012

A Brief Tip on Generating Fractional Factorial Designs in R

October 1, 2012
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A number of marketing researchers use the orthoplan procedure in SPSS to generate fractional factorial designs.  It is not surprising, then, that I received a number of questions concerning the recent article in the Journal of Statistical Software by Hideo Aizaki on “Basic Functions for Supporting an Implementation of Choice Experiments in R.”  To summarize their issues,...

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Example 10.4: Multiple comparisons and confidence limits

October 1, 2012
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Example 10.4: Multiple comparisons and confidence limits

A colleague is a devotee of confidence intervals. To him, the CI have the magical property that they are immune to the multiple comparison problem-- in other words, he feels its OK to look at a bunch of 95% CI and focus on the ones that appear to exclude the null. This though...

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When Russell 2000 is Low Vol

October 1, 2012
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When Russell 2000 is Low Vol

Continuing in my exploration of the Russell 2000 (Russell 2000 Softail Fat Boy), I thought I would try to approach the topic with a low volatility paradox mindset.  Since 2005, beta of the Russell 2000 compared to the S&P 500 has exceeded 1.2 ...

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Level fit summaries can be tricky in R

October 1, 2012
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Level fit summaries can be tricky in R

Model level fit summaries can be tricky in R. A quick read of model fit summary data for factor levels can be misleading. We describe the issue and demonstrate techniques for dealing with them.When modeling you often encounter what are commonly called categorical variables, which are called factors in R. Possible values of categorical variablesRelated posts:

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How does my computer know what language I am using? – An approach of statistical learning (Language, Computer Science)

October 1, 2012
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How does my computer know what language I am using? – An approach of statistical learning (Language, Computer Science)

Quick and Easy Subsetting

October 1, 2012
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Quick and Easy Subsetting

Public health datasets can be enormous and difficult to look at.  Often it is great to be able to only look at specific parts of the dataset, or to only run analysis on a specific part of a dataset.  There are two ways that you can subset a d...

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Rcpp 0.9.14

October 1, 2012
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Another release of Rcpp has just appeared on CRAN and was just uploaded to Debian.It addresses yet another issue we had on OS X and should hopefully put the build issues to rest. Three new (vectorized) sugar functions were added, along with some ne...

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Making random, equally-sized partitions

October 1, 2012
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Making random, equally-sized partitions

Sometimes, as with cross-validation, one needs to generate k partitions, each with an equal number of observations. There are probably an infinite number of ways this could be done in R, but the Gist below illustrates one way to do it in four lines, w...

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How to add a benchmark to a variance matrix

October 1, 2012
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How to add a benchmark to a variance matrix

There is a good way and a bad way to add a benchmark to a variance matrix that will be used for optimization and similar operations.  Our examination sheds a little light on the process of variance matrix estimation in this realm. Role of benchmarks Investing Benchmarks are common in investment management.  It’s my opinion … Continue reading...

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