R Reference Card - Getting help, Input and output, Data creation, Slicing and extracting data

Q: How do you search R help for a topic?

Use help.search("topic") to search the help system by topic. Use apropos("topic") to list object names matching a regular expression.

Q: What functions are used to read CSV, delimited text, and fixed-width files?

read.csv("filename", header=TRUE) reads comma-delimited files. read.delim("filename", header=TRUE) reads tab-delimited files. read.fwf(file, widths, header=FALSE, sep="", as.is=FALSE) reads fixed-width formatted data.

Q: How can you index vectors, lists, and matrices in R?

Vectors can use x[n], x[-n], and ranges like x[1:n] or x[c(1,4,2)]. Lists use x[n], nx[[n]], and named access like x[["name"]]. Matrices use x[i,j] for elements, x[i,] for a row, and x[,j] for a column.

Oct 13, 2026

Upload by Noah

Concise R reference covering essential help functions, searching and starting the HTML help system, and quick summaries for common objects. Provides core input and output guidance including loading data, reading tables/CSV/DELIM, fixed-width formats, saving objects, formatted printing, and file/connection usage for clipboard and standard streams. Includes data creation utilities such as sequences, replication, data.frame, list and array constructors, plus slicing and indexing patterns for vectors, lists, matrices, and data frames.

LanguageEnglish

CategoryPresentations

FormatPDF

Pages4

Reading Time2 min

AccessFree to download

Getting help

Help search and documentation

Object inspection and summarization

Input and output

Reading data (tables/CSV/DELIM/fixed-width)

Saving and formatting output

Files, connections, and clipboard

Data creation

Sequences and replication

data.frame, lists, arrays, and factors

Combining and expanding structures

Slicing and extracting data

Vector and list indexing

Matrix and data-frame indexing

Variable conversion

R Reference Card by Tom Short, EPRI PEAC, [tshort@epri-peac.com 2004-11-07](tshort@epri-peac.com 2004-11-07) Granted to the public [domain. See www.Rpad.org](domain. See www.Rpad.org) for the source and latest version. Includes material from R for Beginners by Emmanuel Paradis (with permission) . Getting help Most R functions have online documentation. help(topic) documentation on topic?topic id. [help.search](help.search) ("topic") search the help system apropos("topic") the names of all objects in the search list matching the regular expression ”topic” help.start() start the HTML version of helpstr(a) display the internal *str*ucture of an R object summary(a) gives a “summary” of a, usually a statistical summary but it is generic meaning it has different operations for different classes of a ls() show objects in the search path; specify pat="pat" to search on a pattern ls.str() str() for each variable in the search path dir() show ﬁles in the current directory methods(a) shows S3 methods ofa methods(class=class(a)) lists all the methods to handle objects of class a Input and output load() load the datasets written with save data(x) loads speciﬁed data sets library(x) load add-on packages read .table(file) reads a ﬁle in table format and creates a data frame from it; the default separator sep="" is any whitespace; use header=TRUE to read the ﬁrst line as a header of column names; use [as.is=TRUE](as.is=TRUE to prevent character vectors)[ to prevent character vectors](as.is=TRUE to prevent character vectors) from being converted to factors; use comment.char="" to prevent "\#" from being interpreted asa comment; use skip=n to skip n lines before reading data; see the help for options on row naming, NA treatment, and others read .csv("filename",header=TRUE) id. but with defaults set for reading comma-delimited ﬁles read .delim("filename",header=TRUE) id. but with defaults set for reading tab-delimited ﬁles 􀁿 read.fwf(file,widths,header=FALSE,sep="",[as.is=FALSE](as.is=FALSE) ) read a table offixed width formatted data into a ’data.frame’; widths is an integer vector, giving the widths ofthe ﬁxed-width ﬁelds save(file, . . . ) saves the speciﬁed objects (...) in the XDR platform independent binary format save.image(file) saves all objects cat( . . . , file="", sep=" ") prints the arguments after coercing to character; sep is the character separator between arguments print(a, . . . ) prints its arguments; generic, meaning it can have differ ent methods for different objects format(x, . . . ) format an R object for pretty printing write .table(x,file="",row .names=TRUE,col .names=TRUE, sep=" ") prints x after converting to a data frame; ifquote is TRUE, character or factor columns are surrounded by quotes ( "); sep is the ﬁeld separator; eol is the end-of-line separator; na is the string for missing values; use col.names=NA to add a blank column header to get the column headers aligned correctly for spreadsheet input sink(file) output to file, until sink() Most ofthe I/O functions have a file argument. This can often be a character string naming a ﬁle or a connection. file="" means the standard input or output. Connections can include ﬁles, pipes, zipped ﬁles, and R variables. On windows, the ﬁle connection can also be used with description = "clipboard". To read a table copied from Excel, use x < -read.delim("clipboard") To write a table to the clipboard for Excel, use write.table(x,"clipboard",sep="nt",col.names=NA) For database interaction, see packages RODBC, DBI, RMySQL, RPgSQL, and ROracle. See packages XML, hdf5, netCDF for reading other ﬁle formats. Data creation c( . . . ) generic function to combine arguments with the default forming a vector; with recursive=TRUE descends through lists combining all elements into one vector from:to generates a sequence; “:” has operator priority; 1:4 + 1 is “2,3,4,5” seq(from,to) generates a sequence by= speciﬁes incremen

FAQs

How do you search R help for a topic?

Use help.search("topic") to search the help system by topic. Use apropos("topic") to list object names matching a regular expression.

What functions are used to read CSV, delimited text, and fixed-width files?

read.csv("filename", header=TRUE) reads comma-delimited files. read.delim("filename", header=TRUE) reads tab-delimited files. read.fwf(file, widths, header=FALSE, sep="", as.is=FALSE) reads fixed-width formatted data.

How can you index vectors, lists, and matrices in R?

Vectors can use x[n], x[-n], and ranges like x[1:n] or x[c(1,4,2)]. Lists use x[n], nx[[n]], and named access like x[["name"]]. Matrices use x[i,j] for elements, x[i,] for a row, and x[,j] for a column.

Oct 13, 2026

Upload by Noah