Articles by Luis

R for inquisition

December 21, 2012 | Luis

A post on high-dimensional arrays by @isomorphisms reminded me of APL and, more generally, of matrix languages, which took me back to inquisitive computing: computing not in the sense of software engineering, or databases, or formats, but of learning by poking problems through a computer. I like languages not because ... [Read more...]

Matrix Algebra Useful for Statistics

December 16, 2012 | Luis

I was having a conversation with an acquaintance about courses that were particularly useful in our work. My forestry degree involved completing 50 compulsory + 10 elective† courses; if I had to choose courses that were influential and/or really useful they would be Operations Research, Economic Evaluation of Projects, Ecology, 3 Calculus and 2 ... [Read more...]

When R, or any other language, is not enough

December 14, 2012 | Luis

This post is tangential to R, although R has a fair share of the issues I mention here, which include research reproducibility, open source, paying for software, multiple languages, salt and pepper. There is an increasing interest in the reproducibility … Continue reading → [Read more...]

R pitfalls #4: redefining the basics

December 13, 2012 | Luis

I try to be economical when writing code; for example, I tend to use single quotes over double quotes for characters because it saves me one keystroke. One area where I don’t do that is when typing TRUE and FALSE … Continue reading → [Read more...]

More sense of random effects

November 17, 2012 | Luis

I can’t exactly remember how I arrived to Making sense of random effects, a good post in the Distributed Ecology blog (go over there and read it). Incidentally, my working theory is that I follow Scott Chamberlain (@recology_), who follows … Continue reading → [Read more...]

Overlay of design matrices in genetic analysis

October 12, 2012 | Luis

I’ve ignored my quantitative geneticist side of things for a while (at least in this blog) so this time I’ll cover some code I was exchanging with a couple of colleagues who work for other organizations. It is common to … Continue reading → [Read more...]

Scraping pages and downloading files using R

October 1, 2012 | Luis

I have written a few posts discussing descriptive analyses of evaluation of National Standards for New Zealand primary schools.The data for roughly half of the schools was made available by the media, but the full version of the dataset is … Continue reading → [Read more...]

Some regressions on school data

September 26, 2012 | Luis

Eric and I have been exchanging emails about potential analyses for the school data and he published a first draft model in Offsetting Behaviour. I have kept on doing mostly data exploration while we get a definitive full dataset, and … Continue reading → [Read more...]

New Zealand school performance: beyond the headlines

September 24, 2012 | Luis

I like the idea of having data on school performance, not to directly rank schools—hard, to say the least, at this stage—but because we can start having a look at the factors influencing test results. I imagine the opportunity in … Continue reading → [Read more...]

(Unsurprisingly) users default to the defaults

September 19, 2012 | Luis

Oddities tend to jump out when one uses software in a daily basis. The situation is even clearer when using software for teaching: many more people looking at it with fresh eyes. Let’s say that we are fitting a simple … Continue reading → [Read more...]

Mid-September flotsam

September 14, 2012 | Luis

This is one of those times of the year: struggling to keep the head above the water, roughly one month before the last lecture of the semester. On top trying to squeeze trips, meetings and presentations in between while dealing … Continue reading → [Read more...]

Suicide statistics and the Christchurch earthquake

September 5, 2012 | Luis

Suicide is a tragic and complex problem. This week New Zealand’s Chief Coroner released its annual statistics on suicide, which come with several tables and figures. One of those figures refers to monthly suicides in the Christchurch region (where I … Continue reading → [Read more...]

m x n matrix with randomly assigned 0/1

August 28, 2012 | Luis

Today Scott Chamberlain tweeted asking for a better/faster solution to building an m x n matrix with randomly assigned 0/1. He already had a working version: Now, I’m the first to acknowledge that I’ve never got the ‘apply’ family of … Continue reading → [Read more...]

Mid-August flotsam

August 20, 2012 | Luis

Reached mid-semester point, with quite a few new lectures to prepare. Nothing extremely complicated but, as always, the tricky part is finding a way to make it meaningful and memorable. Sometimes, and this is one of those times, I sound … Continue reading → [Read more...]

INLA: Bayes goes to Norway

August 15, 2012 | Luis

INLA is not the Norwegian answer to ABBA; that would probably be a-ha. INLA is the answer to ‘Why do I have enough time to cook a three-course meal while running MCMC analyses?”. Integrated Nested Laplace Approximations (INLA) is based … Continue reading → [Read more...]

Careless comparison bites back (again)

August 6, 2012 | Luis

When running stats labs I like to allocate a slightly different subset of data to each student, which acts as an incentive for people to do their own work (rather than copying the same results from a fellow student). We … Continue reading → [Read more...]

Early August flotsam

August 5, 2012 | Luis

Back teaching a couple of subjects and it’s the constant challenge to find enough common ground with students so one can push/pull them to the other side of new concepts. We are not talking about complex hierarchical models using mixed … Continue reading → [Read more...]

Split-plot 2: let’s throw in some spatial effects

July 30, 2012 | Luis

Disappeared for a while collecting frequent flyer points. In the process I ‘discovered’ that I live in the middle of nowhere, as it took me 36 hours to reach my conference destination (Estoril, Portugal) through Christchurch, Sydney, Bangkok, Dubai, Madrid … Continue reading → [Read more...]

Split-plot 1: How does a linear mixed model look like?

June 24, 2012 | Luis

I like statistics and I struggle with statistics. Often times I get frustrated when I don’t understand and I really struggled to make sense of Krushke’s Bayesian analysis of a split-plot, particularly because ‘it didn’t look like’ a split-plot to … Continue reading → [Read more...]
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