# Monthly Archives: January 2013

## Regression on categorical variables

January 30, 2013
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$N_{x,t}\sim\mathcal{P}(E_{x,t}\cdot \exp[\alpha_x+\beta_x \kappa_t + \gamma_x \delta_{t-x}])$

This morning, Stéphane asked me tricky question about extracting coefficients from a regression with categorical explanatory variates. More precisely, he asked me if it was possible to store the coefficients in a nice table, with information on the variable and the modality (those two information being in two different columns). Here is some code I did to produce the...

## Approaching the Zero Bound – Bonds

January 30, 2013
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As bonds approach the artificial zero bound, where do we go next especially after the record setting +30% in 2011?  The rolling 250-day total return has rarely gone negative since the inception of the Vanguard Funds VBMFX and VUSTX.  I am int...

## The magic empty bracket

January 30, 2013
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$The magic empty bracket$

I have been working with R for some time now, but once in a while, basic functions catch my eye that I was not aware of… For some project I wanted to transform a correlation matrix into a covariance matrix. Now, since cor2cov does not exist, I thought about “reversing” the cov2cor function (stats:::cov2cor). Inside

## Speed up for loops in R

January 30, 2013
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Are your for loops too slow in R ? Are loops that should take seconds actually taking hours ? As I found out recently, how you structure your code can make a huge difference in execution times. Fortunately making a few small changes to your code can speed up these loops by several orders of

## R’s range and loop behaviour: Zero, One, NULL

January 30, 2013
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One of the most common pattern in programming languages is to ability to iterate over a given set (a vector usually) by using 'for' loops. In most modern scripting languages range operations is a build in data structure and trivial to use with 'for' lo...

## Building a package in RStudio is actually very easy

January 30, 2013
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So, you’ve written some code and you use it routinely. Now you’ve written some code and you’d like to use version control to ensure that development continues in a robust fashion. You do that and you use Github or something so that not only are changes tracked, but the general public receives the benefit of

## The three-dots construct in R

January 30, 2013
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There is a mechanism that allows variability in the arguments given to R functions.  Technically it is ellipsis, but more commonly called “…”, dots, dot-dot-dot or three-dots. Basics The three-dots allows: an arbitrary number and variety of arguments passing arguments on to other functions Arbitrary arguments The two prime cases are the c and list The post The...

## A shiny app to display the human body map dataset

January 30, 2013
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There was quite a lot of buzz around when the guys from Rstudio launched Shiny, a new web framework for R that promises to “make it super simple for R users like you to turn analyses into interactive web applications … Continue reading →

## Using Boost’s foreach macro

January 30, 2013
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Boost provides a macro, BOOST_FOREACH, that allows us to easily iterate over elements in a container, similar to what we might do in R with sapply. In particular, it frees us from having to deal with iterators as we do with std::for_each and std::transform. The macro is also compatible with the objects exposed by Rcpp. Side note: C++11 has introduced...

## Converting a list to a data frame

January 30, 2013
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There are many situations in R where you have a list of vectors that you need to convert to a data.frame. This question has been addressed over at StackOverflow and it turns out there are many different approaches to completing this task. Since I encou...