As I am working with large gene expression matrices (microarray data) in my job, it is sometimes important to look at the correlation in gene expression of different genes. It has been shown that by calculating the Pearson correlation between genes, one can identify (by high values, i.e. > 0.9) genes that share a common 
I cringe when I see research proposals that describe a sophisticated statistical approach, yet do not evaluate this approach in their power/precision/sample size planning. It's often the case that a simplified version of the proposed statistical approach is used instead. Presumably, this is due to the limited availability of power/precision/sample size planning software for sophisticated
When I want to insert figures generated in R into a LaTeX document, it looks better if I first remove the white space around the figure. Unfortunately, R does not make this easy as the graphs are generated to look good on a screen, not in a document. There are two things that can be done to fix this...
Since at some point I had trouble with a conflict between knitr and the latex package textpos, I used the lesser Sweave in Another Experiment with R and Sweave. I ran the Sweave2knitr command and discovered that textpos and knitr play well togeth...
(This paragraph is pure rant; feel free to skip it) I have been looking forward to the one-column LaTeX style of The R Journal, and it has arrived eventually. Last time I mentioned "it does not make sense to sell the cooked shrimps"; actually there is ...
During the course, we have seen that it is natural to assume that not only the individual claims frequency can be explained by some covariates, but individual costs too. Of course, appropriate families should be considered to model the distribution of the cost , given some covariates .Here is the dataset we’ll use, > sinistre=read.table("http://freakonometrics.free.fr/sinistreACT2040.txt", + header=TRUE,sep=";") > sinistres=sinistre...
Question The mean safety audit score of ACME Co. stores in New York (n=200) was 74.3pts February last year. Suppose we decided to sample 22 out of the 200 stores one year later. We find that the sample mean is 78.6pts and the sample standard deviation is 3.2pts. Can we reject the null hypothesis that
Last week, we’ve seen how to take into account the exposure to compute nonparametric estimators of several quantities (empirical means, and empirical variances) incorporating exposure. Let us see what can be done if we want to model a binomial response. The model here is the following: , the number of claims on the period is unobserved the number of...
The links to previous parts are listed here. (Part 1, Part 2, Part 3). In this part, I tried to recreate the examples in sections A.3.1 of the computational appendix in the reaction engineering book (by Rawlings and Ekerdt). Solving a … Continue reading →
Yesterday, I was uploading some old posts to complete the migration (I get back to my old posts, one by one, to check links of pictures, reformating R codes, etc). And I re-discovered a post published amost 2 years ago, on nuns and Hell’s Angels in an airplaine. It reminded me an old probability problem (that might be known...
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).
