introduction to r - from rstudio to ggplot

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R: Introduction

Olga Scrivner

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Acknowledgments

Center of Excellence for Women in Technology (CEWiT)

Social Science Research Commons (SSRC)

Cyberinfrastructure for Network Science Center (CNS)

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Outline

1 Intro to RStudio

2 Using R scripts

3 Installing packages

4 R objects

Data types

Vectors

Lists

5 Getting help

6 Data visualization

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Materials Needed

1 https://languagevariationsuite.wordpress.com/

2017/08/07/r-introduction-sph-workshop/

2 intro.r

3 plotting.r

4 Movie metadata csv

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https://languagevariationsuite.wordpress.com/2017/08/07/r-introduction-sph-workshop/

https://languagevariationsuite.wordpress.com/2017/08/07/r-introduction-sph-workshop/

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R software

R is a free software for statistical analysis, text mining andgraphics.

To install R on Window:

1 Download the binary file for R https://cran.

r-project.org/bin/windows/base/R-3.3.1-win.exe

2 Open the downloaded .exe file and Install R

To install R on Mac:

1 Download the appropriate version of .pkg filehttps://cran.r-project.org/bin/macosx/

2 Open the downloaded .pkg file and Install R

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https://cran.r-project.org/bin/windows/base/R-3.3.1-win.exe

https://cran.r-project.org/bin/windows/base/R-3.3.1-win.exe

https://cran.r-project.org/bin/macosx/

R Studio

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R Studio

RStudio is a free user interface for R.

1 Install the appropriate RStudio version https:

//www.rstudio.com/products/rstudio/download/

2 Run it to install R-studio

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https://www.rstudio.com/products/rstudio/download/

https://www.rstudio.com/products/rstudio/download/

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R Studio Structure

For more details - see handout RStudio101 (by OscarTorres-Reyna)

http://dss.princeton.edu/training/RStudio101.pdf7 / 67

http://dss.princeton.edu/training/RStudio101.pdf

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Organizing Your Files

Option 1

Create new script / Open existing script

Set up your working directory

Keep your datafiles in this directory (easy access)

Or use command file.choose()

Or remember the path to datafiles

Option 2

Create new project/ Open existing project

Do not have to set up working directory

Keep your datafiles in the project directory

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Creating Projects

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Creating R Script

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Saving R Script

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Closing and Opening Scripts

Close R File: File → Close

Open R File: File → Open

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Editing Script: Font and Size

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RStudio - Full View

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Learning R Syntax

variable stores values

Assignment operator: <-

x <- 5

y <- 6

A valid name for variable must start with a letter.

Name can contain letters, numbers, underscores, and dot.

Valid names Invalid names

mydata

my data

mydata2

my.data

mydata!

my data

2mydata

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Script Flow

1 Create two variables

x <- 5y <- 6

2 run executes commands:

- Place cursor anywhere on the first line - click run- Place cursor on the second line - click run

3 Console displays the execution

4 Right top

- Environment stores objects- History stores commands

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Values

1 Change value of y to 6.5

2 Examine objects in environment

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Comments

1 Comments are not executed

2 Comments are preceded by # (hash tag)

3 Type a comment above your first line of code

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Print()

Function print() prints the value into your console

Inside the parenthesis you type the name of your variable

Examine the output in the console

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Characters versus Numeric Values

Numbers are without quotation marks:

x <- 5

Characters are enclosed in quotation marks:

z <-“a”

Arithmetic operations with numerics

In the console type x*y, press enter

In the console type z*w, press enter

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Logical Values

1 TRUE, FALSE - upper case, no quotes

2 Add comment # logical values

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Data Types

1 Data types:

LogicalNumericCharacter

2 Function class() identifies the class type

3 Type in the script

4 Examine the console

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Vector - Basic Types

Vector: A sequence of data elements of the same basic type

Numeric

c(2, 3, 5)

Logical

c(TRUE, FALSE, TRUE)

Character string

c("aa", "bb", "cc")

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Vector

In the script create two vectors:

Examine the environment

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Length

Function length() of a vector

length(v1)

Create a vector with words:

mywords <-c(“These”, “are”,“my”,“words”)

1 How many words in mywords?

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Index Slicing

1. [1:3] - consecutive elements: one, two, three

2. [c(1,3)] - only the elements one and three

3. [-2] - all except the element number two

Extract the first and the second elements

Extract all except the first element

Extract the first and the fourth elements

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Indexing

How to extract certain elements from a vector?

What is the first word in mywords?

- mywords[1]

What are the first and second words in mywords?

- mywords[1:2]

What are the first and third words in mywords?

- mywords[c(1,3)]

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Combining Vectors - Strings

vector1 <- c("my", "first", "vector")

vector2 <- c("my", "second", "vector")

vector3 <- c(vector1, vector2)

print(vector3)

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Vectors - Arithmetic Operations

Click RUN to execute each line

v1 <- c(1, 3, 6)

v2 <- c(2, 4, 6)

v1*v2

v1+v2

v1/v2

vector1*vector2 - what will happen?

vector3 <- c(vector1, vector2)

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Vectors - paste

paste(vector1, "+", vector2, sep = " ")

paste(vector1, "+", vector2, sep = "")

paste(vector1, "+", vector2, collapse = " ")

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Usefulness of paste - Create a Plot Title

Scenario: You are going to create a plot with x (Age Groups)and y (Frequency) with the following titleMy plot: Frequency of Age Groups

y <- "Frequency"

x <- "Age Groups"

title <- "My plot:"

c(title,y,"of",x)

paste(title,y,"of",x,collapse=" ")

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Lists

List: a vector that can contain different types

mylist <- list(vector1, v1)

print(mylist)

[[ ]] - index for lists

[ ] - index for vectors32 / 67

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List versus Vector

Vectors contain the objects of the same type:

- v1 <- c(“a”,“b”,“c”)

- v2 <- c(1,2,3,4)

Lists contain different types of objects

Vector uses c() function

List uses list() function

Create mylist:

miniquiz: What are the data types in mylist?

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Indexing List

1 Print list: print(mylist)

2 Remember vector indices [ ]?

3 List will use [[ ]]

4 Type mylist[[1]]

5 Type mylist[[7]]

6 How to access the first numberinside the list object?

7 mylist[[7]][1]

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Operators: Arithmetic

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Operators: Logical

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Operators: Logical

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a <- 1

b <- 2

a > b

a <= 2

a != b

a == b

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Installing Packages

In your bottom left window - go to Packages

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Selecting Packages

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Package = Library

In your Packages window scroll down until you see languageRand click inside the box:

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Package Content

To access package description and its content, click on thepackage name.

New window Help will open up:

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Accessing Info from Packages

Scroll down and select languageR-package

You will see the list of available functions from this package

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Quick Help

Type in the console (bottom left):

?length

Instead of Run - click enter-key

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File Formats

1 CSV, Excel Movie metadata.csv

2 TXT NY Times.txt

3 PDF Article.pdf

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CSV, Excel, SAS, SPSS Data

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CSV

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CSV Data

Close data view:

colnames(movie metadata)

nrow(movie metadata)

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Visualization

“The science of analytical reasoningfacilitated by visual interactive interfaces”

(Thomas and Cook, 2005)

“Visual analytics integrates new computational andtheory-based tools with innovative interactive techniquesand visual representations to enable human-information

discourse” (Thomas and Cook, 2005)

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Graphical Elements

PointsLinesSurfacesVolumes

https://www.interaction-design.org/literature/article/

visual-mapping-the-elements-of-information-visualization

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https://www.interaction-design.org/literature/article/visual-mapping-the-elements-of-information-visualization

https://www.interaction-design.org/literature/article/visual-mapping-the-elements-of-information-visualization

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Graphical Properties

Graphical properties - make graphical elements “more (orindeed less) noticeable to the eye and/or valuable to the user ofthe representation”

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Data Mapping (Mackinley, 1987)

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Nominal

Quantitative

Ordinal

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Mapping: Quantitative Data

Based on slides by John Hart https://www.coursera.org/learn/datavisualization

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https://www.coursera.org/learn/datavisualization

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Mapping Perceptual Accuracy

Color Hue - wheel colorSaturation - intensity

Mackinlay, 1987 - https://research.tableau.com/sites/default/files/p110-mackinlay.pdf53 / 67

https://research.tableau.com/sites/default/files/p110-mackinlay.pdf

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Bar Chart

The value of a column in the data set. This is done withstat=“identity”, which leaves the y values unchanged.The count of cases for each group - each x valuerepresents one group.

http://www.cookbook-r.com/Graphs/Bar_and_line_graphs_(ggplot2)/

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Creating a Bar Chart - Sample

http:

//www.cookbook-r.com/Graphs/Bar_and_line_graphs_(ggplot2)/

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Creating a Bar Chart - Sample

http:


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Creating a Bar Chart - Values

http:


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Creating a Bar Chart - Counts

To get a bar graph of counts, we do not map a variable to y,and we use stat=“count”http://www.cookbook-r.com/Graphs/Bar_and_line_graphs_(ggplot2)/

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Creating a Bar Chart - Counts

http:


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Title

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Scatter Plot

Scatter charts show the relationship between two variables. Toconstruct a scatter chart, we need observations that consist ofpairs of variables

Based on slides by John Hart https://www.coursera.org/learn/datavisualization61 / 67

https://www.coursera.org/learn/datavisualization

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Creating Scatter Plot

http://www.r-graph-gallery.com/272-basic-scatterplot-with-ggplot2/

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http://www.r-graph-gallery.com/272-basic-scatterplot-with-ggplot2/

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Bubble Chart

A bubble chart is a type of scatter chart in which the size ofthe data marker corresponds to the value of a third variable;consequently, it is a way to plot three variables in twodimensions

https://www.tableau.com/sites/default/files/media/which_chart_v6_final_0.pdf

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https://www.tableau.com/sites/default/files/media/which_chart_v6_final_0.pdf

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Creating Bubble Plot

https://plot.ly/r/bubble-charts/

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Creating Bubble Plot


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Practice - Flashcards

IVMOOC flashcards app

IU IVMOOC course

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Practice-DataCamp

1 Sign up for a free DataCamp.com account

2 Search Introduction to R course

3 Complete and receive a Certificate!

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introduction to r - from rstudio to ggplot

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