Introduction to R
Lukáš Lehotský
Courses' objectives
• Introduction to basic concepts and techniques of data manipulation, qualitative comparative analysis and text analysis with R
• Not a course on general methodology or research design
• Not a course on programing in R, but includes programming introduction interlinked with data manipulation
R: advantages
• Extremely powerful
• Freeware and open source
• Integrated
• Transparent/easy to find errors
• Modular (re-usability of codes)
• Fast compared to "point-and-click" programs
R: disadvantages
• Steep learning curve compared to "point-and-click" programs
• Data preparation possibly demanding
• Inconsistencies across packages
• Package-dependent (some particular operations not implemented)
• Slower compared to other programming languages in large operations
R community / resources
• R package / library manuals
• R site: http://cran.r-project.org
• Community forums
• htt p: //sta c kove rf I o w. co m
• http://www.statmethods.net
• http://www.r-bloggers.com
• Youtube videos https://www.voutube.com/watch?v=qHfSTRNg6i
R: not a silver bullet
• Some tasks are cumbersome in R
• Other software much better in some particular tasks
• Sophisticated scripting does not offset poor research design
R: focus on logic
• Any programming language is just very condensed and formalized speech
• The most complicated part is designing the procedure of what needs to be done
• Writing the actual script is fairly easy
Introduction to R
• You should have two programs installed on computer
• R
• R Studio
• Both have to be installed to run R Studio
• We are going to use R Studio
• More convenient to work with
RStudio
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R version 3.4.1 (2917-66-39)  --  "Single Candle"
Copyright (C) 2917 The R Foundation for Statistical Computing
Platform: x86_64-w64-mingw32/x64 (64-bit)
R is free software and comes with ABSOLUTELY NO WARRANTY. You are welcome to redistribute it under certain conditions. Type 'licenseQ' or 'licenceQ' for distribution details.
R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.
Type 'demoO' for some demos,  'helpO' for on-line help, or 1 help.start()' for an HTML browser interface to help. Type  'q()'  to quit R.
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R version 3.4.1 (2917-66-39)  --  "Single Candle"
Copyright (C) 2917 The R Foundation for Statistical Computing
Platform: x86_64-w64-mingw32/x64 (64-bit)
R is free software and comes with ABSOLUTELY NO WARRANTY. You are welcome to redistribute it under certain conditions. Type 'licenseQ' or 'licenceQ' for distribution details.
R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.
Type 'demoO' for some demos,  'helpO' for on-line help, or 1 help.start()' for an HTML browser interface to help. Type  'q()'  to quit R.
>
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Introduction to R: console vs. script
• Console provides instant input
• Short bits of code executed one by one
• Very similar to other console programs (e.g. Linux)
• Enter runs the command
• Faster
• Does not contain history
• Scripts
• Complete piece of code
• Executed at once
• Executed bit by bit
• CTRL + SHIFT + N creates new script in R Studio
• Ctrl + Enter runs the selected piece of code
O RStudio
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Object-oriented programming
Object
• object: instance of a certain data class that can be manipulated according set of procedures (methods)
one <- 1
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			Name		Description	Version
		User Library				A
			assertthat		Easy Pre and Post Assertions	0.2.0
1S     | (Top Level) t	R Script t 1					
		□	audio		Audio Interface for R	0.1-5
Console						
		□	beepr		Easily Play Notification Sounds on any Platform	1.2
						
		□	BH		Boost C+ + Header Files	1.62.0-1
		□	bindr		Parametrized Active Bindings	0.1
		□	bindrcpp		An 'Repp' Interface to Active Bindings	0.2
		□	bitops		Bitwise Operations	1.0-6
		□	Cairo		R graphics device using cairo graphics library for creating high-quality bitmap [PNG, JPEG, TIFF], vector [PDF, SVG, PostScript) and display [X11 and Win32) output	
		□	chron		Chronological Objects which can Handle Dates and Times	2.3-50
		□	colorspace		Color Space Manipulation	1.3-2
		□	CL "1		A Modern and Flexible Web Client for R	23.1
		□	data.table		Extension of'data,frame'	1.10-4
		n	dichromat		Color Schemes for Dichromats	2.0-0        © v I I
						
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		Install    © Update			1 IQ,	11 @
			Name		Description	Version
		User Library				A
			assertthat		Easy Pre and Post Assertions	0.2.0
1S     | (Top Level) t	R Script t 1					
		□	audio		Audio Interface for R	0.1-5
Console						
		□	beepr		Easily Play Notification Sounds on any Platform	1.2
						
		□	BH		Boost C+ + Header Files	1.62.0-1
		□	bindr		Parametrized Active Bindings	0.1
		□	bindrcpp		An 'Repp' Interface to Active Bindings	0.2
		□	bitops		Bitwise Operations	1.0-6
		□	Cairo		R graphics device using cairo graphics library for creating high-quality bitmap [PNG, JPEG, TIFF], vector [PDF, SVG, PostScript) and display [X11 and Win32) output	
		□	chron		Chronological Objects which can Handle Dates and Times	2.3-50
		□	colorspace		Color Space Manipulation	1.3-2
		□	CL "1		A Modern and Flexible Web Client for R	23.1
		□	data.table		Extension of'data,frame'	1.10-4
		n	dichromat		Color Schemes for Dichromats	2.0-0        © v I I
						
RStudio
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User Library
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Easy I
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0.2.0
I  I dichromat
Color Schemes for Dichromats
2.0-0
Environment History	= n
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Files    Plots    Packages    Help    Viewer J	
)| Install    (t) Update X	l 1 (55
Name                  Description m	Version
□	audio	Ausi^hlerface for R	0.1-5
□	beepr	^^zasily Play Notification Sounds on any Platform	1.2
	BH	Boost C+ + Header Files	1.62.0-1 O
□	bindr	Parametrized Active Bindings	0.1
□	bindrcpp	An 'Repp' Interface to Active Bindings	0.2
□	bitops	Bitwise Operations	1.0-6
□	Cairo	R graphics device using cairo graphics library for creating high-quality bitmap [PNG, JPEG, TIFF), vector [PDF, SVG, PostScript) and display [X11 and Win32) output	1.5-9
□	chron	Chronological Objects which can Handle Dates and Times	2.3-50 ©
□	colorspace	Color Space Manipulation	1.3-2
□	CL "1	A Modern and Flexible Web Client for R	23.1
□	data.table	Extension of'data,frame'	1.10.4
Object: what is it?
• Object is container
• Element is anything in container - a peach
• To reuse elements, they must be stored as objects
• Any name defined by user
• Remain the same unless overwritten
• Must be removed by user as well
Object: creating/storing objects
		
Object	<-	Element
(container)		(peach)
Object: use
• Once objects exist, you may use it as whole or its elements for various operations
• It may be reused again and again
• Functions may be applied
one <- 1
one + one
[11 2
RStudio
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Install    © Update		1 IQ,		11 <3
	Name	Description	Version	
User Library				A
□	assertthat	Easy Pre and Post Assertions	0.2.0	©
□	audio	Audio Interface for R	0.1-5	e
	beepr	Easily Play Notification Sounds on any Platform	1.2	©
□	BH	Boost C+ + Header Files	1.62.0-1	©
□	bindr	Parametrized Active Bindings	0.1	©
□	bindrcpp	An 'Repp' Interface to Active Bindings	0.2	©
□	bitops	Bitwise Operations	1.0-6	
□	Cairo	R graphics device using cairo graphics library for creating high-quality bitmap [PNG, JPEG, TIFF], vector [PDF, SVG, PostScript) and display [X11 and Win32) output	1.5-9	
	chron	Chronological Objects which can Handle Dates and Times	2.3-50	©
□	colorspace	Color Space Manipulation	1.3-2	©
□	CL "1	A Modern and Flexible Web Client for R	23.1	©
□	data.table	Extension of'data,frame'	1.10.4	©
n	dichromat	Color Schemes Jor Dichronats	2.0-0	
RStudio
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> one <- 1
> one + one [1] 2
>
Files	Plots    Packages    Help Vie		Ler		
Install Update			I*		I I s
	Name	Description j	f Version		
User Library					A
□	assertthat	Easy Pre and#ost Assertions		0.2.0	©
□	audio	Audio IntsJFace for R		0.1-5	e
	beepr	Easilyjrey Notification Sounds on any ~->\amrn		1.2	©
□	BH M	(Boost C + + Header Files		1.62.0-1	©
□	blndr ^^^^	Parametrized Active Bindings		0.1	©
	^rloYcpp	An 'Repp' Interface to Active Bindings		0.2	©
□	bitops	Bitwise Operations		1.0-6	
□	Cairo	R graphics device using cairo graphics library for creating high-quality bitmap [PNG, JPEG, TIFF), vector [PDF, SVG, PostScript) and display [X11 and Win32) output		1.5-9	
	chron	Chronological Objects which can Handle Dates and Times		2.3-50	©
□	colorspace	Color Space Manipulation		1.3-2	©
□	CL "1	A Modern and Flexible Web Client for R		23.1	©
□	data.table	Extension of'data,frame'		1.10.4	©
n	dichromat	Color Schemes Jor Dichronats		2.0-0	
Object: use
• Any output of any operation needs to be stored
• new object may be created
• existing object may be rewritten
one <- 1
one + one
[11 2
two <- one + one
two [11 2
o	RStudio	- °D
File   Edit   Code  View  Plots  Session   Build   Debug   Profile  lools Help		
CH Ä*l Q 01 Qli^Goto file/function          1 @ -    Addins »		^  Project: (None) »
		
<3j Untitledl* x	aD      Environment History	= n
1 <£L 1 H □ Source onSave  1 <i        - 1 O 1 *	t^Run 1 |*J* 1 [_*► Source   '1  ^   1   ^ S 1 £3* Import Data set - 1 ^	= List - 1 @
1   one <- 1	Global Environment »	10.              —\ \
6:1       (Top Level)
Console -/ 1
> one <- 1
> one + one [1] 2
> two <- one + one
>
Files	Plots    Packages    Help Viewer				
Ol Install    (£) Update			i O		
	Name	Description	I Version		
User Library					A
□	assertthat	Easy Pre and Post Assertions m		0.2.0	
□	audio	Audio Interface for R m		0.1-5	©
	beepr	Easily Play Notification Sounds m\ any Platform f		1.2	©
□	BH	Boost C+ + Header Files^r		1.62.0-1	©
□	bindr	Parametrized Actiyafcindings		0.1	©
□	bindrcpp	An 'RcppJ|()efface to Active Bindings		0.2	©
□ .	bitops ^^^^^^	*Frwise Operations		1.0-6	
TT	Cairo	R graphics device using cairo graphics library for creating high-quality bitmap [PNG, JPEG, TIFF), vector [PDF, SVG, PostScript) and display [X11 and Win32) output		1.5-9	
	chron	Chronological Objects which can Handle Dates and Times		2.3-50	©
□	colorspace	Color Space Manipulation		1.3-2	©
□	CL "1	A Modern and Flexible Web Client for R		23.1	©
□	data.table	Extension of'data,frame'		1.10.4	©
n	dichromat	Color Schemes Jor Dichronats		2.0-0	
RStudio
Eile  Edit   Code  View  Plots  Session   Build   Debug   Profile  lools Help
<fH -I & ' I Q 01 Ü I I * Go to file/functio
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1 one <- 1
2
3 one + one
4
5 two <- one + one
6
7 two
8 I
8:'
(Top Level) i
Console -/ 1
> one <- 1
> one + one [1] 2
> two <- one + one
> two [1] 2
>
R Script :
Environment		History	= n		
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Values					
one			l		
two			2		
					
					
Files	Plots	Packages    Help Viewer			= n
)| Install    (t) Update			1 IQ,		
	Name		Description	Version	
User Library					A
□	assertthat		Easy Pre and Post Assertions	0.2.0	©
□	audio		Audio Interface for R	0.1-5	e
	beepr		Easily Play Notification Sounds on any Platform	1.2	©
□	BH		Boost C+ + Header Files	1.62.0-1	©
□	bindr		Parametrized Active Bindings	0.1	©
□	bindrcpp		An 'Repp' Interface to Active Bindings	0.2	©
□	bitops		Bitwise Operations	1.0-6	
□	Cairo		H graphics device using cairo graphics library for creating high-quality bitmap [PNG, JPEG, TIFF), vector [PDF, SVG, PostScript) and display [X11 and Win32) output	1.5-9	
	chron		Chronological Objects which can Handle Dates and Times	2.3-50	©
□	colorspace		Color Space Manipulation	1.3-2	©
□	CL "1		A Modern and Flexible Web Client for R	23.1	©
□	data.table		Extension of'data,frame'	1.10.4	©
n	dichromat		Color Schemes Jor Dichronats	2.0-0	© v
Function
• Pre-defined methods which allow operations over objects
• To create an object with more than one element, function c () is used
onetofive <- c(l,3,5,4,2)
• Any object may be manipulated with a function
sort(onetofive) [1]  1 2 3 4 5
Function: arguments
• To extend functionality, functions have pre-defined arguments
• Arguments extend the functionality of function
• Some functions have many arguments, some none
• Results of the function must always be stored in the environment
sort(onetofive) [1]  1 2 3 4 5
sort(onetofive,  decreasing = TRUE) [1]  5 4 3 2 1
onetofive <- sort(onetofive,  decreasing = TRUE)
Function: syntax
• f unctionname ()  indicates function
sqrt(9) [1] 3
• Structure is function (argl,  arg2, ...)
sample(0:100,   10,   rep = FALSE) [1]   48 50 37 94 42 39 21  19 63 95
• If help is necessary, just add question mark or use function
help() in front of the function name
?sample() help(sample)
10.27
Data class
• Properties of elements inside the object
• Numeric - continuous numeric data
• -1,0.5, 10.27
• Integer - discrete numeric data
• -l, o, l
• Character - string values
• "anythingWithinQuotes"
• Logical - boolean output of logical operation
• TRUE/FALSE, NA
• Factor
• "agree", "disagree", "neutral"
Data class
Data class
• Sometimes, data elements are ambiguous
• Distinctions important for computer
• It is useful to explore data class of any object
• This is not a necessary step
• R comes with pre-defined behavior on classes - sometimes counterintuitive (e.g. in data sets, character variables are by default converted to factors)
• Useful in debugging the code
• If necessary, class can be converted/changed
class(10.27) [1] "numeric"
Data class: conversion of classes
as.numeric(10.27) [1] 10.27
as.integer(10.27) [1 ] 10
as.character(-1) [1 ]   "-1 "
as.numeric("anything") [1 ] NA
Warning message: NAs Introduced by coercion
5 > 10
[1] FALSE
as.character(5 > 10) [1] "FALSE"
Tips and tricks
• Keyboard hacks
• For Czech keyboard and Win machine users, Right Alt (AltGr) allows you to type some special characters (AltGr + < for <)
• Script hacks
• # allows you to write comments in scripts
• When writing code, R will automatically add closing bracket, as well as closing quote symbol
• Tab will finish the name of function or argument in R Studio - try typing help( and press Tab
Practice
• Create a new script
• Define 5 objects of your own liking (including object with more than one element)
• Get a class of each of the following items: 5, " 5 ", NA,
TRUE, "true", NULL
• Calculate the equation
(5.5*4) + (7.5*2.
12)
using R objects
12
7
• Try to get a square root of number 254
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