# Blog Archives

## More on logging the outcome

March 4, 2011
By

This one does my head in. I do it fairly regularly, lots of people do, but I find everytime it comes to interpreting the results I have to slow it right down and go step by step. Answer: When you log the outcome, then on the original scale, for all else constant, Y will be

## Anova – Type I/II/III SS explained

March 2, 2011
By

Not my post, just bookmarking this. It’s from http://goanna.cs.rmit.edu.au/~fscholer/anova.php ANOVA (and R) The ANOVA Controversy ANOVA is a statistical process for analysing the amount of variance that is contributed to a sample by different factors. It was initially derived by R. A. Fisher in 1925, for the case of balanced data (equal numbers of observations

## Graphing – margins, titles, mtext, workspace

February 21, 2011
By

This is a great post, very true, not enough of R’s graphics are well displayed online to really see how to achieve what the often ambiguous ‘help’ information suggests. http://research.stowers-institute.org/efg/R/Graphics/Basics/mar-oma/index.htm I particularly find “mtext(“lol”, outer=T)” to be particularly useful (requires “oma=c(2,2,2,2)” or similar). http://addictedtor.free.fr/graphiques/ This site is somewhat of the way there, but I’ve found

## Child health metrics

February 20, 2011
By

In analysis of Child Health data, generally z-scores or percentile groupings are used as children do not growth is not linear. The CDC (Center for Disease Control and Prevention) have released tables of data for calculating these z-scores and percentiles, and here are some scripts for R to calculate these in your sample. CLICK HERE

## Mixed models – Part 2: lme lmer

February 15, 2011
By

Getting more into mixed models, I’ve been playing around with both nlme::lme and lme4::lmer. http://tolstoy.newcastle.edu.au/R/e2/help/06/10/3345.html was quite a good post at explaining the differences, which from what I gather is largely performance based when using crossed or partially crossed models. In the models I am tinkering with at the moment I am noticing differences in

## Mixed Models – Part 1

February 3, 2011
By

Very brief. Have been exploring mixed models in R using nlme::lme. Am looking forward to understanding them more, they’re going to be used more and more in years to come I’ve no doubt of that. Here are some scripts, very rough, for diagnostics when running simple 2 levels, or models with 1 grouping variable. CLICK