Holcombe:ProgrammingInR

SUPA Sydney University Perception and Action Lab Primer editing help refcard

R is an interactive programming language for statistics. The syntax is very idiosyncratic, and not really in a good way. Try R for programmers for a description. However it may have menu-driven versions maybe available R commander we haven't tried that and another one is pmg GTK maybe here

In the lab we have the book Using R for Introductory Statistics. R_Statistics introduces you to R

R reference cheatsheet, also a file here Media:Matlab-python-xref.pdf‎ that gives equivalent code for doing array operations in MATLAB, Python, and R plot parameters

There is a wiki with some good tips here. Also Data frame tips, list of R websites

Functions in R can only return one parameter. Calling typeof() on a dataframe returns "list"! Delete nearly everything in memory: rm(list = ls())

Examining your data matrix or object, let's say it's called datos

head(datos)
str(datos)

Don't use the function attach. It seems to leave lots of data in the 'environment' that can cause problems later. Also it makes the code harder to understand.

fitting psychometric functions

Malte Kuss hosts the R library PsychoFun on his personal webpage rather than c-ran server. So you must download is package, unzip it, and install it by going to R->Packages&Data->Package Installer->Local Package Directory->Install, go inside the PsychoFun directory you've unzipped, and click Open.

I needed to constrain width of psychometric function to be quite narrow. Prior I was using followed lognormal distribution. Then if want mode to be say .1, have to feed it a mean parameter of -2.3 because ln(.1) = -2. Unfortunately the PsychoFun code doesn't allow using a negative parameter for that prior, so I had to change the code. To do so, you go into the downloaded version of PsychoFun folder before you install it, where you can find PsychoFun.R in the R subdirectory. I commented out line 56. Then have to reinstall with Install manager inside R, after in my case first deleting original PsychoFun installation in /Library/Frameworks/R.framework/Versions/2.10/Resources/library/

doing ANOVAs etc

some aov (ANOVA) explanation

R will assume factor is regressor if numeric

I think I had too many error terms reducing error terms

Dealing with circular data

von Mises vs. wrapped Gaussian,

see Swindale, N. V. (1998). Orientation tuning curves: empirical description and estimation of parameters. Biol Cybern, 78(1), 45-56.

Setting up a proxy in R on a Mac

The easiest way to set up a proxy is simply to create a file called ".Rprofile" in your user directory (~ or Users/username/) with the line:

 Sys.setenv(http_proxy=”http://username:password@tcdproxy.tcd.ie:8080″)

Then restart R. This information (and more) can be found on Ken Benoit's webpage

For Sydney Uni, use:

 Sys.setenv(http_proxy=”http://www-cache.usyd.edu.au:8080″)