From a recent mailing from Stata (highlighting by me): Funnily enough, there is a Daniel Rubin, a bio-informatics person here at Stanford.
Monthly Archives: March 2010
In a nls star things might be different than the lm planet…
The nls() function has a well documented (and discussed) different behavior compared to the lm()’s. Specifically you can’t just put an indexed column from a data frame as an input or output of the model. > nls(data ~ c + expFct(data,beta), data = time.data, + start = start.list) Error in parse(text = x) : unexpected
Clustering the world’s diets
Cluster Analysis is a useful technique for classifying the members of a group (people, events, measurements, etc) into "similar" groups. How "similar" is defined depends on the application, but generally involves looking at a number of attributes of the group. For example, we could cluster people by looking at their skin color, hair type, facial features, perhaps even genetic...
In case you missed it: February roundup
In case you missed them, here are some articles from last month of particular interest to R users. We announced the availability on YouTube of "What is R", a 4-part video based on a recent webcast I hosted. We announced a webinar I hosted on REvolution's debugger for R (a recorded replay is now available). We linked Salvio Rodrigues...
Strategy: what if SPY & VIX are up?
Recently, I was busy testing the following strategy: If SPY and VIX daily returns are positive, then short SPY at close and keep it for one day. The strategy is dump simple and it has very good feature – short side. There are not so many successful short side strategies. For testing purpose I used daily Yahoo
Using Regular Expressions in R: Case Study in Cleaning a BibTeX Database
I recently had to clean up a BibTeX database containing around 1,000 references. One of the clean up tasks was to ensure that page numbers were separated with en-dashes as opposed to hyphens. This post sets out how I used regular expressions in R to co...
Rcpp 0.7.8
Version 0.7.8 of the Rcpp R / C++ interface classes is now on CRAN and in Debian. As of right now. Debian has already built packages for eight more architectures; and CRAN has built the Windows binary. Oh, and cran2deb had Debian packages for 'testing'...
Rcpp 0.7.8
Version 0.7.8 of the Rcpp R / C++ interface classes is now on CRAN and in Debian. As of right now. Debian has already built packages for eight more architectures; and CRAN has built the Windows binary. Oh, and cran2deb had Debian packages for 'testin...
principal components and image reconstruction
Jeff Lewis at UCLA told me he teaches principal components with an image reconstruction example. This got me inspired to try it myself. A snapshot appears below, showing how the image quality improves quickly with a relatively small number of principal components. A full, Sweaved write up is here, making use of the biOps package
Learning R by video
For those people who prefer to be shown how to do something rather than read the instructions, there are some videos on using R available online. Here are the ones I know about. Please add links to other similar resources in the comments. R videos Learn R Toolkit What is R? from Revolution Analytics R
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).
