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Base R
Cheat Sheet
RStudio® is a trademark of RStudio, Inc. • CC BY Mhairi McNeill • mhairihmcneill@gmail.com Learn more at web page or vignette • package version • Updated: 3/1 5 Input Ouput Description df <- read.table(‘file.txt’) write.table(df, ‘file.txt’) Read and write a delimited text file. df <- read.csv(‘file.csv’) write.csv(df, ‘file.csv’) Read and write a comma separated value file. This is a special case of read.table/ write.table. load(‘file.RData’) save(df, file = ’file.Rdata’) Read and write an R data file, a file type special for R.
?mean
Get help of a particular function.
help.search(‘weighted mean’)
Search the help files for a word or phrase.
help(package = ‘dplyr’)
Find help for a package.
Getting Help
Accessing the help files More about an object
str(iris)
Get a summary of an object’s structure.
class(iris)
Find the class an object belongs to.
Programming For Loop for (variable in sequence){ Do something }
Example
for (i in 1:4){ j <- i + 10 print(j) } While Loop while (condition){ Do something }
Example
while (i < 5){ print(i) i <- i + 1 } If Statements if (condition){ Do something } else { Do something different }
Example
if (i > 3){ print(‘Yes’) } else { print(‘No’) } Functions function_name <- function(var){ Do something return(new_variable) }
Example
square <- function(x){ squared <- x*x return(squared) } a == b (^) Are equal a > b Greater than a >= b Greater than or equal to is.na(a)^ Is missing a != b (^) Not equal a < b (^) Less than a <= b Less than or equal to is.null(a)^ Is null Conditions Creating Vectors c(2, 4, 6) 2 4 6 Join elements into a vector 2:6 2 3 4 5 6 An integer sequence seq(2, 3, by=0.5) 2.0 2.5 3.0 A complex sequence rep(1:2, times=3) 1 2 1 2 1 2 Repeat a vector rep(1:2, each=3) 1 1 1 2 2 2 Repeat elements of a vector
Using Libraries
install.packages(‘dplyr’)
Download and install a package from CRAN.
library(dplyr)
Load the package into the session, making all its functions available to use.
dplyr::select
Use a particular function from a package.
data(iris)
Load a built-in dataset into the environment. Vectors Selecting Vector Elements
x[ 4 ] The fourth element.
x[- 4 ] All but the fourth.
x[ 2 : 4 ] Elements two to four.
x[-( 2 : 4 )]
All elements except
two to four.
x[c( 1 , 5 )]
Elements one and
five.
x[x == 10 ]
Elements which
are equal to 10.
x[x < 0 ]
All elements less
than zero.
x[x %in%
c( 1 , 2 , 5 )]
Elements in the set
By Position
By Value
Named Vectors
x[‘apple’]
Element with
name ‘apple’.
Reading and Writing Data
Working Directory
getwd()
Find the current working directory (where inputs are found and outputs are sent).
setwd(‘C://file/path’)
Change the current working directory.
Use projects in RStudio to set the working
directory to the folder you are working in.
Vector Functions
sort(x)
Return x sorted.
rev(x)
Return x reversed.
table(x)
See counts of values.
unique(x)
See unique values.
RStudio® is a trademark of RStudio, Inc. • CC BY Mhairi McNeill • mhairihmcneill@gmail.com • 844-448-1212 • rstudio.com Learn more at web page or vignette • package version • Updated: 3/1 5 Lists Matrixes Data Frames Maths Functions Types (^) Strings Factors Statistics Distributions as.logical TRUE, FALSE, TRUE Boolean values (TRUE or FALSE). as.numeric 1, 0, 1 Integers or floating point numbers. as.character '1', '0', '1' Character strings. Generally preferred to factors. as.factor '1', '0', '1', levels: '1', '0' Character strings with preset levels. Needed for some statistical models. Converting between common data types in R. Can always go from a higher value in the table to a lower value.
> a <- 'apple'
> a
[1] 'apple'
The Environment Variable Assignment
ls() List all variables in the
environment.
rm(x) Remove x from the
environment.
rm(list = ls()) Remove all variables from the
environment.
You can use the environment panel in RStudio to
browse variables in your environment.
factor(x)
Turn a vector into a factor. Can
set the levels of the factor and
the order.
m <- matrix(x, nrow = 3 , ncol = 3 )
Create a matrix from x.
ww ww ww
m[ 2 , ] - Select a row
m[ , 1 ] - Select a column
m[ 2 , 3 ] - Select an element
ww ww ww ww ww ww
t(m)
Transpose
m %*% n
Matrix Multiplication
solve(m, n)
Find x in: m * x = n
l <- list(x = 1:5, y = c('a', 'b'))
A list is collection of elements which can be of different types.
l[[2]] l[1] l$x l['y']
Second element
of l.
New list with
only the first
element.
Element named
x.
New list with
only element
named y.
df <- data.frame(x = 1:3, y = c('a', 'b', 'c'))
A special case of a list where all elements are the same length.
t.test(x, y)
Preform a t-test for
difference between
means.
pairwise.t.test
Preform a t-test for
paired data.
log(x) (^) Natural log. sum(x) (^) Sum. exp(x) (^) Exponential. mean(x) (^) Mean. max(x) (^) Largest element. median(x) (^) Median. min(x) (^) Smallest element. quantile(x) (^) Percentage quantiles. round(x, n) (^) Round to n decimal places. rank(x) (^) Rank of elements. signif(x, n) (^) Round to n significant figures. var(x) (^) The variance. cor(x, y) (^) Correlation. sd(x) (^) The standard deviation.
x y
1 a
2 b
3 c
Matrix subsetting
df[2, ]
df[ , 2]
df[2, 2]
List subsetting
df$x df[[2]]
cbind - Bind columns.
rbind - Bind rows.
View(df)
See the full data
frame.
head(df)
See the first 6
rows.
Understanding a data frame
nrow(df)
Number of rows.
ncol(df)
Number of
columns.
dim(df)
Number of
columns and
rows.
Plotting Dates See the^ lubridate^ library.
Also see the ggplot2 library.
Also see the stringr library.
Also see the
dplyr library.
plot(x)
Values of x in
order.
plot(x, y)
Values of x
against y.
hist(x)
Histogram of
x.
Random
Variates
Density
Function
Cumulative
Distribution
Quantile
Normal rnorm^ dnorm^ pnorm^ qnorm
Poison rpois^ dpois^ ppois^ qpois
Binomial rbinom^ dbinom^ pbinom^ qbinom
Uniform runif^ dunif^ punif^ qunif
lm(x ~ y, data=df)
Linear model.
glm(x ~ y, data=df)
Generalised linear model.
summary
Get more detailed information
out a model.
prop.test
Test for a
difference
between
proportions.
aov
Analysis of
variance.
paste(x, y, sep = ' ') (^) Join multiple vectors together. paste(x, collapse = ' ') (^) Join elements of a vector together. grep(pattern, x) (^) Find regular expression matches in x. gsub(pattern, replace, x) (^) Replace matches in x with a string. toupper(x) (^) Convert to uppercase. tolower(x) (^) Convert to lowercase. nchar(x) (^) Number of characters in a string.
cut(x, breaks = 4)
Turn a numeric vector into a
factor but ‘cutting’ into
sections.
