* You are viewing Posts Tagged ‘statistics’

A lightweight object browser for R

The following post is based on information originally found here: http://r.789695.n4.nabble.com/Object-Browser-td2594912.html
If you use the basic R GUI and you can manage to remember what sorts of objects you have in the workspace more than 5 seconds after you enter them, you’ve got a better short term memory than I do. But if you constantly lose track of what variables, data frames, model objects and so forth you have in your R session, a separate “object browser” window can be a godsend.

Diehard R command line users just use the ls() command to list the objects in memory, and get a … Continue Reading

Book Review: Mixed Effects Models and Extensions in Ecology with R


Mixed Effects Models and Extensions in Ecology with R
Zuur, A.F., Ieno, E.N., Walker, N., Saveliev, A.A., Smith, G.M.
Springer, 2009

Somewhere along the line you probably realized that your undergraduate statistics classes didn’t quite cover the breadth of topics you’d end up needing for dealing with your data. The time constraints of a typical quarter or semester-long biostats class often leave you only scratching the surface of all of the issues you need to consider when analyzing a typical ecological data set. That’s … Continue Reading

Book Review: A Beginner’s Guide to R

A Beginner's Guide to R

A Beginner’s Guide to R

Alain F. Zuur, Elena N. Ieno, Erik H.W.G. Meesters
Springer, 2009

So you’ve decided to start learning R. Probably because someone in your institution, typically a gentleman with an unkempt beard who likes to rail on about open source software, has convinced you to abandon the comfortable GUI-driven statistics program you learned in undergrad. But it quickly becomes apparent that leaving the familiar point-and-click interface of JMP or Minitab or (horrors) Excel for the text-driven world of R isn’t as simple as downloading … Continue Reading

Book Review: R in a Nutshell

R in a Nutshell
R in a Nutshell
Joseph Adler
O’Reilly Media, 2010

If you’re looking for an introduction to the R computing language and statistical platform, R in a Nutshell, by Joseph Adler, may be worth a look. This book is a member of O’Reilly Media’s “In a Nutshell” series that may be familiar to you if you dabble in programming. The goal of the book is to introduce the reader to many aspects of the R language, from the basic architecture and syntax of R to some of the many available … Continue Reading

Calculating LT50 (median lethal temperature, aka LD50) quickly in R

Say you’ve got a bunch of survival/mortality data from an experiment. Maybe you exposed batches of snails to various high temperatures for a few hours, and recorded the number alive and dead in each batch at the end. Now you’d like to report the median lethal temperature (or perhaps a lethal dosage if you were injecting stuff into critters). We can do this fairly quickly using R statistical software to perform a logistic regression and back-calculate the LT50.

This assumes that you already have R installed on your computer and you know how to fire it up.

To start with, we need … Continue Reading