# Articles by Luis

### Cute Gibbs sampling for rounded observations

October 31, 2016 |

I was attending a course of Bayesian Statistics where this problem showed up: There is a number of individuals, say 12, who take a pass/fail test 15 times. For each individual we have recorded the number of passes, which can go from 0 to 15. Because of confidentiality issues, we are presented with ... [Read more...]

### Mucking around with maps, schools and ethnicity in NZ

December 7, 2014 |

I’ve been having a conversation for a while with @kamal_hothi and @aschiff on maps, schools, census, making NZ data available, etc. This post documents some basic steps I used for creating a map on ethnic diversity in schools at the census-area-unit level. This “el quicko” version requires 3 ingredients: ... [Read more...]

### Comment on Sustainability and innovation in staple crop production in the US Midwest

July 28, 2014 |

After writing a blog post about the paper “Sustainability and innovation in staple crop production in the US Midwest” I decided to submit a formal comment to the International Journal of Agricultural Sustainability in July 2013, which was published today. As far as I know, Heinemann et al. provided a rebuttal ... [Read more...]

### Sometimes I feel (some) need for speed

July 11, 2014 |

I’m the first to acknowledge that most of my code could run faster. The truth of the matter is that, in essence, I write ‘quickies’: code that will run once or twice, so there is no incentive to spend days or hours in shaving seconds of a computation. Most ... [Read more...]

### Less wordy R

March 11, 2014 |

The Swarm Lab presents a nice comparison of R and Python code for a simple (read ‘one could do it in Excel’) problem. The example works, but I was surprised by how wordy the R code was and decided to check if one could easily produce a shorter version. The ... [Read more...]

### R as a second language

January 5, 2014 |

Imagine that you are studying English as a second language; you learn the basic rules, some vocabulary and start writing sentences. After a little while, it is very likely that you’ll write grammatically correct sentences that no native speaker would use. You’d be following the formalisms but ignoring ... [Read more...]

### Teaching linear models

January 2, 2014 |

I teach several courses every year and the most difficult to pull off is FORE224/STAT202: regression modeling. The academic promotion application form in my university includes a section on one’s ‘teaching philosophy’. I struggle with that part because I suspect I lack anything as grandiose as a philosophy ... [Read more...]

### Statistics unplugged

December 27, 2013 |

How much does statistical software help and how much it interferes when teaching statistical concepts? Software used in the practice of statistics (say R, SAS, Stata, etc) brings to the party a mental model that it’s often alien to students, while being highly optimized for practitioners. It is possible ... [Read more...]

### Using Processing and R together (in OS X)

December 19, 2013 |

I wanted to develop a small experiment with a front end using the Processing language and the backend calculations in R; the reason why will be another post. This post explained the steps assuming that one already has R and Processing installed: Install the Rserve package. This has to be ... [Read more...]

### Excel, fanaticism and R

December 16, 2013 |

This week I’ve been feeling tired of excessive fanaticism (or zealotry) of open source and R in general. I do use a fair amount of OSS and pushed for the adoption of R in our courses; in fact I do think OSS is a good thingTM. I do not ... [Read more...]

### Flotsam 13: early July links

July 9, 2013 |

Man flu kept me at home today, so I decided to do something ‘useful’ and go for a linkathon: Ed Yong discusses the effect of subject expectations in psychology experiments Nice Results, But What Did You Expect? At the beginning there was another article on The placebo phenomenon, and another ... [Read more...]

### My take on the USA versus Western Europe comparison of GM corn

July 4, 2013 |

A few days ago I came across Jack Heinemann and collaborators’ article (Sustainability and innovation in staple crop production in the US Midwest, Open Access) comparing the agricultural sectors of USA and Western Europe‡. While the article is titled around the word sustainability, the main comparison stems from the use ... [Read more...]

### Flotsam 12: early June linkathon

June 1, 2013 |

A list of interesting R/Stats quickies to keep the mind distracted: A long draft Advanced Data Analysis from an Elementary Point of View by Cosma Shalizi, in which he uses R to drive home the message. Not your average elementary point of view. Good notes by Frank Davenport on ... [Read more...]

### Analyzing a simple experiment with heterogeneous variances using asreml, MCMCglmm and SAS

May 17, 2013 |

I was working with a small experiment which includes families from two Eucalyptus species and thought it would be nice to code a first analysis using alternative approaches. The experiment is a randomized complete block design, with species as fixed effect and family and block as a random effects, while ... [Read more...]

### Subsetting data

May 6, 2013 |

At School we use R across many courses, because students are supposed to use statistics under a variety of contexts. Imagine their disappointment when they pass stats and discovered that R and statistics haven’t gone away! When students start working with real data sets one of their first stumbling ... [Read more...]

### Learning to code in R

April 25, 2013 |

It used to be that the one of the first decisions to make when learning to program was between compiled (e.g. C or FORTRAN) and interpreted (e.g. Python) languages. In my opinion these days one would have to be a masochist to learn with a compiled language: the ... [Read more...]

### Flotsam 11: mostly on books

April 16, 2013 |

‘No estaba muerto, andaba the parranda’† as the song says. Although rather than partying it mostly has been reading, taking pictures and trying to learn how to record sounds. Here there are some things I’ve come across lately. I can’t remember if I’ve recommended Matloff’s The ... [Read more...]

### Remembering server installation details

January 8, 2013 |

I’ve been moving part of my work to university servers, where I’m just one more peasant user with little privileges. In exchange, I can access the jobs from anywhere and I can access multiple processors if needed. Given that I have a sieve-like memory, where configuration details quickly ... [Read more...]

### An R wish list for 2013

December 29, 2012 |

First go and read An R wish list for 2012. None of the wishes came through in 2012. Fix the R website? No, it is the same this year. In fact, it is the same as in 2005. Easy to find help? Sorry, next year. Consistency and sane defaults? Coming soon to a ... [Read more...]

### My R year

December 23, 2012 |

End-of-year posts are corny but, what the heck, I think I can let myself delve in to corniness once a year. The following code gives a snapshot of what and how was R for me in 2012. outside.packages.2012 [Read more...]
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