Notes on R

Sadly, my (increasinly extensive) notes were lost in a file-copying mishap. Let this be a lesson to everyone else: back up your work!! :)

For examples, stuff you're supposed to type in is listed like this; output from R is listed like this.

Misc. Notes

c( values....) - combine: Puts all the arguments into a single vector
stack( frame): From the documentation: "Stacking vectors concatenates multiple vectors into a single vector along with a factor indicating where each observation originated. Unstacking reverses this operation."; Example:
list1 = c( 1, 2, 3)
list2 = c( 3, 4, 5)
allLists = data.frame(list1, list2)
stack(allLists)
values ind
1 1 list1
2 2 list1
3 3 list1
4 3 list2
5 4 list2
6 5 list2

getwd( ) / setwd( "path" )

Gets the current working directory, or sets it.

data( "filename" )

Reads data from a file, into memory. From the docs:

Currently, four formats of data files are supported:

files ending ‘.R’ or ‘.r’ are source()d in, with the R working directory changed temporarily to the directory containing the respective file. (data ensures that the utils package is attached, in case it had been run via utils::data.)
files ending ‘.RData’ or ‘.rda’ are load()ed.
files ending ‘.tab’, ‘.txt’ or ‘.TXT’ are read using read.table(..., header = TRUE), and hence result in a data frame.
files ending ‘.csv’ or ‘.CSV’ are read using read.table(..., header = TRUE, sep = ";"), and also result in a data frame.

Boxplot( data ): Draws box-and-whisker a plot. If data is a list, draws a single plot. If data is a frame, draws one plot per data list the frame contains, side-by-side.