Monthly Archives: July 2012

Estimating required hospital bed capacity

July 23, 2012
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Estimating required hospital bed capacity

Estimating required hospital bed capacity requires a thorough analysis. There are a lot of ways of approaching a capacity requirement problem, but I think we can agree that a simple spreadsheet analysis just won't cut it. The approach described in this post makes use of discrete-event simulation and, just to clarify, makes abstraction from a lot of variables which should be taken into consideration in...

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Modeling Trick: Impact Coding of Categorical Variables with Many Levels

July 23, 2012
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Modeling Trick: Impact Coding of Categorical Variables with Many Levels

One of the shortcomings of regression (both linear and logistic) is that it doesn’t handle categorical variables with a very large number of possible values (for example, postal codes). You can get around this, of course, by going to another modeling technique, such as Naive Bayes; however, you lose some of the advantages of regression Related posts:

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Computing the degree of dependency (jointness) among explanatory variables using BMS

July 23, 2012
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Capturing the dependence between explanatory variables in the posterior distribution while implementing a Bayesian analysis is crucial. Taking such a dependence into account reveals the sensitivity of posterior distributions of parameters to depen...

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Third year wrap-up

July 23, 2012
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Third year wrap-up

July marks the end of three years of blogging for us. By our count, we've posted 121 examples across the first three years. We aim to be helpful and interesting.As always, it's hard to get a sense of our readership. At the time we wrote this, Feedbur...

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XLConnect 0.2-0

July 23, 2012
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XLConnect 0.2-0

Mirai Solutions GmbH (http://www.mirai-solutions.com) is very pleased to announce the release of XLConnect 0.2-0, which can be found at CRAN. As one of the updates, XLConnect has moved to the newest release of Apache POI: 3.8. Also, the lazy evaluation … Continue reading →

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R Optimization Test

R Optimization Test

I have tested several R optimization functions before: nlm, optim(Nelder-Mead), optim(BFGS), optim(SANN), nlminb, optim (L-BFGS-B) for a eight-parameter Vasicek interest rate model, overall I find that for my setting, nlminb is the best and all R func...

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Two Free Sets of Methods Lectures

July 23, 2012
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I provide links to two (free, publicly available) graduate level political methodology classes by Justin Esarey (Rice University) and Gary King (Harvard University). Both classes focus on statistical theory and modeling in R.

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A comparison of some heuristic optimization methods

July 23, 2012
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A comparison of some heuristic optimization methods

A simple portfolio optimization problem is used to look at several R functions that use randomness in various ways to do optimization. Orientation Some optimization problems are really hard. In these cases sometimes the best approach is to use randomness to get an approximate answer. Once you decide to go down this route, you need … Continue reading...

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Map biodiversity records with rgbif and ggmap packages in R

July 23, 2012
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Map biodiversity records with rgbif and ggmap packages in R

When I attended usrR! 2012 last month, there was an interesting presentation by Dr. David Kahle about the package ggmap. It is a package built over ggmap2 and helps us map spatial data over online maps like Google maps or Open Street Maps. I decided to give ggmap package a try with biodiversity data. So

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Announcing eeptools

July 22, 2012
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The LDS_TOOLS package for R has been replaced by the new eeptools package. I am renaming the package for a number of reasons. First, LDS is a technical industry term in education that stands for Longitudinal Data Systems, which is not commonly known an...

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