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R Commands Cheat Sheet (DRAFT) by

Basic R commands used in a lecture on statistical programming.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Basic Math

exp(x)
Expone­ntial
 
sum(x)
Sum
 
log(x)
Natural log
 
cumsum(x)
Cumulative Sum
 
max(x)
Largest element
 
ceil(x)
Round up
 
min(x)
Smallest element
 
floor(x)
Round down
 
x %% y
Modulo

I/O

write(­data, "­myd­ata.da­t")
Write data as binary.
 
scan("m­yda­ta.d­at­")
Read binary data.
 
getcwd()
Current working directory

Plotting

plot(data)
Plot quick overview.
 
barplot(x, main="T­itl­e", xlab="x label")
Annotated barplot of absolute freque­ncies
 
plot.e­cdf­(data)
Plot ECDF.
 
hist(data, prob=TRUE, breaks=30)
Histogram of relative freque­ncies (30 bins).
 
rug(data)
1D-plot
 
abline­(a,­b,c­ol=­"­red­")
Add a red line with intercept 
a
and slope 
b
to the plot.
 
boxplo­t(d­ata1, data2, ... ,range­=1.5)
Plot boxplots of one or more data sequences in one window. 
range
determines the extend of the whiskers. Default 
range=1.5
, i.e. 1.5 x IQR
 
qqnorm(x)
QQ-Plot against standard normal distri­bution
 
qqPlot(x, dist="u­nif­")
QQ-Plot against any R-standard distri­bution

Vectors

Creating Vectors
 
c(2, 4, 6)
Join elements into a vector
 
2:6
An integer sequence (end inclus­ive!)
 
seq(2,3, by=0.5)
Complex sequence (s. np.lin­space)
 
rep(1:2, 3)
Repeat vector
 
rep(1:2, 3:4)
Repeat each element
Functions
 
sort(x)
Return x sorted.
 
rev(x)
Return x reversed.
 
unique(x)
See unique values.
 
length(x)
Length of x.
Selecting Vector Elements
By Position
 
x[4]
The fourth element
 
x[-4]
All but the fourth.
 
x[2:4]
Elements two to four
 
x[-(2:4)]
All elements except 2 to four
 
x[c(1, 5)]
Elements one and five.
By Value
 
x[x == 10]
All elements equal to 10
 
x[x  < 10]
All elements less than 10.
 
x[x %in% c(1, 2, 5)]
Elements in the given set.
Named Vectors
 
x['apple']
Element with name 'apple'.

Control Flow

for (variable in sequence) {...}
for-loop. If the loop body contains only a single line, the curly brackets can be omitted.
 
while (condi­tion) {...}
while-loop
 
if (i > 5) {

  ...

else {

  ...

}
if-els­e-block
 
foo = functi­on(­arg1, arg2, ...) {

  ...

  return­(var)

}
function

Runs Test of Randomness

rle(x)
Compute the lengths and values of runs of equal values in a vector .
 
rle(x)­$le­ngths
Vector containing the length of each run.
 
rle(x)­$values
Vector of the same length as lengths with the corres­ponding values.

Help

?sqrt
Display docume­ntation of the command 
sqrt
`
 
?'%%'
use quotation marks for special characters

Miscel­laneous

Printing
 
print(­"­Tex­t")
Default print
 
sprint­f("F­orm­atted %s: %.3f", object, mean)
Formatted print
 
(x=3)
enclose an R command with brackets to directly print the result
 
edit(x)
Invoke text editor on R object
 
librar­y(MASS)
Load package MASS

Random Numbers

sample­(1:­3,p­rob­=c(­1/6­,1/­3,1­/2)­,re­pla­ce=­TRU­E,20)
Draw 20 balls, labeled from 1 to 3, from box with replac­ement.
 
r<d­istr. ID>
(n, params)
Draw 
n
numbers from distri­bution 
<distr. ID>
with parameters 
params
(see Distri­butions in R for more details)

Tables

table(­data)
get absolute freque­ncies of values
 
as.num­eri­c(tab); as.vec­tor­(tab)
Extract values and their absolute freque­ncies from table
 
tab/le­ngt­h(data)
Compute relative freque­ncies

Charac­ter­istics of data sequences

mean(x)
Arithmetic mean of the data sequence
 
var(x)
Variance
 
median(x)
Median
 
quanti­le(x, type=7)
Quantile. 
type=7
is the default comput­ation algorithm, i.e. the function returns the value at position 
k=1+p(n-1)
, if this is an integer. Otherwise, R computes a weighted mean of the two neighb­oring integers
 
qunati­le(x, type=1)
General inverse function of the ECDF (smallest p-quan­tile). Largetst p-quantile can be obtained indirectly by slightly increasing p
 
summary(x)
Overview of important measures

Data sets

Intera­cting with data sets
 
col_1 = data$c­ol_­1_name
Access column data
I/O
 
data = read.c­sv(­"­fil­e.c­sv", header­=FALSE, sep="")
Read csv (function arguments similar to that used in pandas)
 
write.c­sv­(data, "­dat­a.c­sv", row.na­mes­=FALSE, sep=" ")
Write data set as csv

Distri­butions in R

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