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Some useful R Functions

Help!

? ?command gives help on the given command, e.g. ?names

Inspecting data

dim dim(d) gives the number of rows and columns in d
names column names in d
head, tail the top/bottom N rows of d
summary A summary of the columns in d
nrow, ncol the number of rows/columns in d

Data characteristics

length length(x) gives the number of items in x
mean, var, sd, median the mean/variance/stdev/median of the values in x

Selecting and subsetting data

d[rows, columns] Select given row(s) and column(s)
d$column, d[[column]] Select given column

Tabulating and plotting

table table(x) gives the frequency of items in x; table(x,y) crosstabulates x and y
plot plot(x, y) gives a scatter plot of x. Use plot(x, y, type='l') to get a line plot
barplot barplot(x) gives a barplot of the values in x
hist hist(x) gives a histogram of x, automatically binning the items
lines lines(x, y) adds a new line to an existing plot

Installing packages and other files

install.packages "Install the given packages. (Can also be done interactively in the packages tab in Rstudio)"
library Load a given package that is already installed
source Run a file (or URL) containing R commands
download.file Download a file from the Internet

Normal distributions

rnorm Generate numbers from a normal distribution
pnorm Proportion of
qqnorm, qqline Plot the Q-Q scatter and normal line of a distribution