R Reference Card (Page 2 of 4) in pdf

unique(x) if x is a vector or a data frame, returns a similar object but with

fft(x) Fast Fourier Transform of an array

nchar(x) number of characters

the duplicate elements suppressed

mvfft(x) FFT of each column of a matrix

Dates and Times

table(x) returns a table with the numbers of the differents values of x

filter(x,filter) applies linear ﬁltering to a univariate time series or

The class Date has dates without times. POSIXct has dates and times, includ-

(typically for integers or factors)

to each series separately of a multivariate time series

ing time zones. Comparisons (e.g.

), seq(), and difftime() are useful.

subset(x, ...) returns a selection of x with respect to criteria (...,

Many math functions have a logical parameter na.rm=FALSE to specify miss-

Date also allows

and . ?DateTimeClasses gives more information. See

typically comparisons: x$V1 < 10); if x is a data frame, the option

ing data (NA) removal.

also package chron.

select gives the variables to be kept or dropped using a minus sign

Matrices

as.Date(s) and as.POSIXct(s) convert to the respective class;

sample(x, size) resample randomly and without replacement size ele-

t(x) transpose

format(dt) converts to a string representation. The default string

ments in the vector x, the option replace = TRUE allows to resample

diag(x) diagonal

format is “2001-02-21”. These accept a second argument to specify a

with replacement

% * % matrix multiplication

format for conversion. Some common formats are:

prop.table(x,margin=) table entries as fraction of marginal table

solve(a,b) solves a %*% x = b for x

Math

solve(a) matrix inverse of a

%a, %A Abbreviated and full weekday name.

sin,cos,tan,asin,acos,atan,atan2,log,log10,exp

rowsum(x) sum of rows for a matrix-like object; rowSums(x) is a faster

%b, %B Abbreviated and full month name.

max(x) maximum of the elements of x

version

%d Day of the month (01–31).

min(x) minimum of the elements of x

colsum(x), colSums(x) id. for columns

%H Hours (00–23).

range(x) id. then c(min(x), max(x))

rowMeans(x) fast version of row means

%I Hours (01–12).

sum(x) sum of the elements of x

colMeans(x) id. for columns

%j Day of year (001–366).

diff(x) lagged and iterated differences of vector x

Advanced data processing

%m Month (01–12).

prod(x) product of the elements of x

%M Minute (00–59).

apply(X,INDEX,FUN=) a vector or array or list of values obtained by

mean(x) mean of the elements of x

%p AM/PM indicator.

applying a function FUN to margins (INDEX) of X

median(x) median of the elements of x

%S Second as decimal number (00–61).

lapply(X,FUN) apply FUN to each element of the list X

quantile(x,probs=) sample quantiles corresponding to the given prob-

%U Week (00–53); the ﬁrst Sunday as day 1 of week 1.

tapply(X,INDEX,FUN=) apply FUN to each cell of a ragged array given

abilities (defaults to 0,.25,.5,.75,1)

%w Weekday (0–6, Sunday is 0).

by X with indexes INDEX

weighted.mean(x, w) mean of x with weights w

%W Week (00–53); the ﬁrst Monday as day 1 of week 1.

by(data,INDEX,FUN) apply FUN to data frame data subsetted by INDEX

rank(x) ranks of the elements of x

%y Year without century (00–99). Don’t use.

merge(a,b) merge two data frames by common columns or row names

var(x) or cov(x) variance of the elements of x (calculated on n 1); if x is

%Y Year with century.

xtabs(a b,data=x) a contingency table from cross-classifying factors

a matrix or a data frame, the variance-covariance matrix is calculated

%z (output only.) Offset from Greenwich; -0800 is 8 hours west of.

aggregate(x,by,FUN) splits the data frame x into subsets, computes

sd(x) standard deviation of x

%Z (output only.) Time zone as a character string (empty if not available).

summary statistics for each, and returns the result in a convenient

cor(x) correlation matrix of x if it is a matrix or a data frame (1 if x is a

form; by is a list of grouping elements, each as long as the variables

vector)

Where leading zeros are shown they will be used on output but are optional

in x

var(x, y) or cov(x, y) covariance between x and y, or between the

on input. See ?strftime.

stack(x, ...) transform data available as separate columns in a data

columns of x and those of y if they are matrices or data frames

frame or list into a single column

cor(x, y) linear correlation between x and y, or correlation matrix if they

unstack(x, ...) inverse of stack()

are matrices or data frames

reshape(x, ...) reshapes a data frame between ’wide’ format with

round(x, n) rounds the elements of x to n decimals

Plotting

repeated measurements in separate columns of the same record and

log(x, base) computes the logarithm of x with base base

plot(x) plot of the values of x (on the y-axis) ordered on the x-axis

’long’ format with the repeated measurements in separate records;

scale(x) if x is a matrix, centers and reduces the data; to center only use

plot(x, y) bivariate plot of x (on the x-axis) and y (on the y-axis)

use (direction=”wide”) or (direction=”long”)

the option center=FALSE, to reduce only scale=FALSE (by default

hist(x) histogram of the frequencies of x

Strings

center=TRUE, scale=TRUE)

barplot(x) histogram of the values of x; use horiz=FALSE for horizontal

pmin(x,y,...) a vector which ith element is the minimum of x[i],

paste(...) concatenate vectors after converting to character; sep= is the

bars

y[i], . . .

string to separate terms (a single space is the default); collapse= is

dotchart(x) if x is a data frame, plots a Cleveland dot plot (stacked plots

pmax(x,y,...) id. for the maximum

an optional string to separate “collapsed” results

line-by-line and column-by-column)

cumsum(x) a vector which ith element is the sum from x[1] to x[i]

substr(x,start,stop) substrings in a character vector; can also as-

pie(x) circular pie-chart

cumprod(x) id. for the product

sign, as substr(x, start, stop) <- value

boxplot(x) “box-and-whiskers” plot

cummin(x) id. for the minimum

strsplit(x,split) split x according to the substring split

sunflowerplot(x, y) id. than plot() but the points with similar coor-

cummax(x) id. for the maximum

grep(pattern,x) searches for matches to pattern within x; see ?regex

dinates are drawn as ﬂowers which petal number represents the num-

union(x,y), intersect(x,y), setdiff(x,y), setequal(x,y),

gsub(pattern,replacement,x) replacement of matches determined

ber of points

is.element(el,set) “set” functions

by regular expression matching sub() is the same but only replaces

stripplot(x) plot of the values of x on a line (an alternative to

Re(x) real part of a complex number

the ﬁrst occurrence.

boxplot() for small sample sizes)

Im(x) imaginary part

tolower(x) convert to lowercase

z) bivariate plot of x and y for each value or interval of

coplot(x˜y

Mod(x) modulus; abs(x) is the same

toupper(x) convert to uppercase

values of z

Arg(x) angle in radians of the complex number

match(x,table) a vector of the positions of ﬁrst matches for the elements

interaction.plot (f1, f2, y) if f1 and f2 are factors, plots the

Conj(x) complex conjugate

of x among table

means of y (on the y-axis) with respect to the values of f1 (on the

convolve(x,y) compute the several kinds of convolutions of two se-

x %in% table id. but returns a logical vector

x-axis) and of f2 (different curves); the option fun allows to choose

quences

pmatch(x,table) partial matches for the elements of x among table

the summary statistic of y (by default fun=mean)

R Reference Card Page 2

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