R Reference Card printable pdf download

R Reference Card

character or factor columns are surrounded by quotes ("); sep is the

Indexing lists

ﬁeld separator; eol is the end-of-line separator; na is the string for

x[n]

list with elements n

missing values; use col.names=NA to add a blank column header to

element of the list

x[[n]]

by Tom Short, EPRI PEAC, 2004-11-07

get the column headers aligned correctly for spreadsheet input

x[["name"]] element of the list named "name"

Granted to the public domain. See for the source and latest

sink(file) output to file, until sink()

x$name

id.

version. Includes material from R for Beginners by Emmanuel Paradis (with

Most of the I/O functions have a file argument. This can often be a charac-

Indexing matrices

permission).

ter string naming a ﬁle or a connection. file="" means the standard input or

element at row i, column j

x[i,j]

output. Connections can include ﬁles, pipes, zipped ﬁles, and R variables.

x[i,]

row i

On windows, the ﬁle connection can also be used with description =

x[,j]

column j

x[,c(1,3)] columns 1 and 3

"clipboard". To read a table copied from Excel, use

Getting help

x["name",] row named "name"

x <- read.delim("clipboard")

Most R functions have online documentation.

To write a table to the clipboard for Excel, use

Indexing data frames (matrix indexing plus the following)

help(topic) documentation on topic

x[["name"]] column named "name"

write.table(x,"clipboard",sep=" t",col.names=NA)

?topic id.

id.

For database interaction, see packages RODBC, DBI, RMySQL, RPgSQL, and

x$name

help.search("topic") search the help system

ROracle. See packages XML, hdf5, netCDF for reading other ﬁle formats.

apropos("topic") the names of all objects in the search list matching

Data creation

the regular expression ”topic”

Variable conversion

help.start() start the HTML version of help

c(...) generic function to combine arguments with the default forming a

str(a) display the internal *str*ucture of an R object

vector; with recursive=TRUE descends through lists combining all

as.array(x), as.data.frame(x), as.numeric(x),

summary(a) gives a “summary” of a, usually a statistical summary but it is

elements into one vector

as.logical(x), as.complex(x), as.character(x),

generic meaning it has different operations for different classes of a

from:to generates a sequence; “:” has operator priority; 1:4 + 1 is “2,3,4,5”

... convert type; for a complete list, use methods(as)

ls() show objects in the search path; specify pat="pat" to search on a

seq(from,to) generates a sequence by= speciﬁes increment; length=

Variable information

pattern

speciﬁes desired length

ls.str() str() for each variable in the search path

seq(along=x) generates 1, 2, ..., length(along); useful for for

is.na(x), is.null(x), is.array(x), is.data.frame(x),

dir() show ﬁles in the current directory

loops

is.numeric(x), is.complex(x), is.character(x),

methods(a) shows S3 methods of a

... test for type; for a complete list, use methods(is)

rep(x,times) replicate x times; use each= to repeat “each” el-

methods(class=class(a)) lists all the methods to handle objects of

length(x) number of elements in x

ement of x each times; rep(c(1,2,3),2) is 1 2 3 1 2 3;

class a

rep(c(1,2,3),each=2) is 1 1 2 2 3 3

dim(x) Retrieve or set the dimension of an object; dim(x) <- c(3,2)

create a data frame of the named or unnamed

dimnames(x) Retrieve or set the dimension names of an object

Input and output

data.frame(...)

arguments; data.frame(v=1:4,ch=c("a","B","c","d"),n=10);

nrow(x) number of rows; NROW(x) is the same but treats a vector as a one-

load() load the datasets written with save

row matrix

shorter vectors are recycled to the length of the longest

data(x) loads speciﬁed data sets

ncol(x) and NCOL(x) id. for columns

list(...)

create a list of the named or unnamed arguments;

library(x) load add-on packages

class(x) get or set the class of x; class(x) <- "myclass"

list(a=c(1,2),b="hi",c=3i);

read.table(file) reads a ﬁle in table format and creates a data

array

with

data

specify

dimensions

unclass(x) remove the class attribute of x

array(x,dim=)

frame from it; the default separator sep="" is any whitespace; use

dim=c(3,4,2); elements of x recycle if x is not long enough

attr(x,which) get or set the attribute which of x

header=TRUE to read the ﬁrst line as a header of column names; use

attributes(obj) get or set the list of attributes of obj

matrix(x,nrow=,ncol=) matrix; elements of x recycle

as.is=TRUE to prevent character vectors from being converted to fac-

factor(x,levels=) encodes a vector x as a factor

Data selection and manipulation

tors; use comment.char="" to prevent "#" from being interpreted as

gl(n,k,length=n * k,labels=1:n) generate levels (factors) by spec-

a comment; use skip=n to skip n lines before reading data; see the

which.max(x) returns the index of the greatest element of x

ifying the pattern of their levels; k is the number of levels, and n is

help for options on row naming, NA treatment, and others

which.min(x) returns the index of the smallest element of x

the number of replications

read.csv("filename",header=TRUE) id. but with defaults set for

rev(x) reverses the elements of x

expand.grid() a data frame from all combinations of the supplied vec-

reading comma-delimited ﬁles

sort(x) sorts the elements of x in increasing order; to sort in decreasing

tors or factors

read.delim("filename",header=TRUE) id. but with defaults set

order: rev(sort(x))

rbind(...) combine arguments by rows for matrices, data frames, and

for reading tab-delimited ﬁles

cut(x,breaks) divides x into intervals (factors); breaks is the number

others

read.fwf(file,widths,header=FALSE,sep="",as.is=FALSE)

of cut intervals or a vector of cut points

cbind(...) id. by columns

read a table of f ixed width f ormatted data into a ’data.frame’; widths

match(x, y) returns a vector of the same length than x with the elements

Slicing and extracting data

is an integer vector, giving the widths of the ﬁxed-width ﬁelds

of x which are in y (NA otherwise)

save(file,...) saves the speciﬁed objects (...) in the XDR platform-

which(x == a) returns a vector of the indices of x if the comparison op-

Indexing vectors

independent binary format

eration is true (TRUE), in this example the values of i for which x[i]

element

x[n]

save.image(file) saves all objects

== a (the argument of this function must be a variable of mode logi-

all but the n

element

x[-n]

cat(..., file="", sep=" ") prints the arguments after coercing to

cal)

ﬁrst n elements

x[1:n]

character; sep is the character separator between arguments

choose(n, k) computes the combinations of k events among n repetitions

elements from n+1 to the end

x[-(1:n)]

print(a, ...) prints its arguments; generic, meaning it can have differ-

= n!

k !k!

x[c(1,4,2)]

speciﬁc elements

ent methods for different objects

na.omit(x) suppresses the observations with missing data (NA) (sup-

x["name"]

element named "name"

format(x,...) format an R object for pretty printing

presses the corresponding line if x is a matrix or a data frame)

x[x > 3]

all elements greater than 3

write.table(x,file="",row.names=TRUE,col.names=TRUE,

na.fail(x) returns an error message if x contains at least one NA

all elements between 3 and 5

x[x > 3 & x < 5]

sep=" ") prints x after converting to a data frame; if quote is TRUE,

x[x %in% c("a","and","the")] elements in the given set

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