GETTING STARTEDsocviz880.co/slides/02_dataviz_s20_getting_started.pdf · eiusmod tempor incididunt...

GETTING STARTED

WE WANT TO DRAW GOOD

DATA GRAPHICSREPRODUCIBLY

Abstraction in SoftwareLess MoreEasy things are awkward

Hard things are straightforward

Really hard things are doable

Easy things are trivial

Hard things are really awkward

Really hard things are impossible

ExcelD3 StataGrid

ggplot

Two ways to use R and ggplot

1. Do Everything in R

Raw Data

Read in, Clean & Analyze

ggplot Figures

2. Just use ggplotTidy

resultsggplot

FiguresStata,

SAS, etc

(Read in, likely with some filtering/transformation)

THE RIGHTFRAME OF MIND

TYPE OUT YOURCODE BY HAND

RSTUDIO

ORGANIZE YOUR PROJECTS

Use RMarkdownTO REPRODUCE

YOUR OWN WORK

This is what we want to end up

with: nicely formatted text,

plots, and tables.

1. Lorem IpsumLorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enimad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

In a Literate Programming

approach to documents,

chunks of code are processed

and replaced with their output

library(ggplot2) tea <- rnorm(100) biscuits <- tea + rnorm(100, 0, 1.3) data <- data.frame(tea, biscuits) p <- ggplot(data, aes(x = tea, y = biscuits)) + geom_point() + geom_smooth(method = "lm") + labs(x = "Tea", y = "Biscuits") + theme_bw() print(p)

# Lorem IpsumLorem ipsum dolor sit amet, consectetur adipisicing elit, sed do *eiusmod tempor* incididunt ut labore et dolore magna aliqua. Ut enimad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.


In a Literate Programming

approach to documents,

chunks of code are processed

and replaced with their output



An Rmd document lets you keep your code and notes

together in plain text

And produce good-looking output in a range of formats




knit in R

notes.Rmd# ReportWe can see this *relationship*in a scatterplot.

As you can see, this plot looks pretty nice.

ReportWe can see this relationshipin a scatterplot.


x

y

notes.html

```{r my-code}p !" ggplot(data, mapping)p + geom_point()

```




knit in R

notes.Rmd# ReportWe can see this *relationship*in a scatterplot.


ReportWe can see this relationshipin a scatterplot.


x

y

notes.docx

```{r my-code}p !" ggplot(data, mapping)p + geom_point()

```

Markdown puts formatting instructions in plain-text documents

# Header

Plain text*italics***bold**`verbatim`

Footnote.[^1][^1]: The footnote.

1. List2. List- Bullet 1- Bullet 2

!" Subhead

Markdown OutputHeader

Plain textitalicsboldverbatim

Footnote.The footnote.

1. List2. List° Bullet 1° Bullet 2

Subhead

1

1

A Markdown Processor turns the marked-up plain

text into actually formatted output in HTML, PDF,

DOCX or other file types.

Header section provides metadata and sets options

Code chunk

Text with Markdown formatting

In RStudio, code chunks can be "played" one at a time

Chunks are replaced by their output when the document is made

Code chunks can have their own names and options

RStudio will do all the work for you

when it comes to processing your document—i.e.,

getting it from plain-text Rmd to

HTML, Word, or PDF.



GETTING ORIENTED

library(tidyverse)

Loading tidyverse: ggplot2 Loading tidyverse: tibble Loading tidyverse: tidyr Loading tidyverse: readr Loading tidyverse: purrr Loading tidyverse: dplyr

The TidyverseDraw graphsNicer data tablesTidy your dataGet data into RCool functional programming stuffAction verbs for manipulating data

library(socviz)

Course-Specific Library

CODE YOU CAN TYPE AND RUN## Inside chunks of code, lines beginning with ## the hash character are comments my_numbers <- c(1, 1, 4, 1, 1, 4, 1)

my_numbers

## [1] 1 1 4 1 1 4 1

OUTPUT

What R Looks Like

FOUR THINGS

TO KNOW ABOUT R

1: Everything has a Name

FALSE TRUE Inf

for if break

function

Some names are forbidden

my_numbersdatap

2. Everything is an Object

my_numbers <- c(1, 2, 3, 1, 3, 5, 25)

letters## [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" [20] "t" "u" "v" "w" "x" "y" "z"

You create objects by assigning a thing to a name

named thing "gets" this stuff

my_numbers <- c(1, 2, 3, 1, 3, 5, 25)

You create objects by assigning a thing to a name

The assignment operator performs the action of creating objects. Use the keyboard shortcut to type it:

option - Macalt - Windows

3. You do things using functions and operators

my_numbers <- c(1, 2, 3, 1, 3, 5, 25)

named thing "gets" this stuff

c() is a function that takes comma-separated numbers or strings and joins them together into a vector

take inputs, perform actions, produce outputs

mean()

Functions have parentheses at the end of their name. This is where the inputs, or arguments go.

mean(x = my_numbers)

Named argument. These names are internal to functions.

"Input is this object. Calculate the mean of it."

Functions

mean(my_numbers)

If you just write the name of the input, R assigns it to the function’s arguments in the order given.

take inputs, perform actions, produce outputsFunctions

You can assign a function’s output to a named object

my_summary <- summary(my_numbers)

my_sd <- sd(my_numbers)

my_summary

my_sd

Objects you create exist until you overwrite or delete them

rm(my_numbers)

my_numbers

my_numbers <- c(1, 2, 3, 1, 3, 5, 25)

Objects are of different classes

class(my_numbers)

numeric

character

factor

Vectorsmatrix

data.frame

tibble

Arrayslm

glm

Models

Things to try on Objects class(my_numbers)table(my_numbers)

x <- c(my_numbers, 5)

mean(c(my_numbers, my_numbers))

Notice that these are functionsHow do x and

y differ?y <- c(my_numbers, "hello")

Functions can be nested, and will be evaluated from the

inside out.

Some operators

+, -, *, /, ^ Arithmetic

<- Assignment ("gets")=or

&, &&, |, ||, ! Logical

%*%, %in%, %>% Special

<, >, <=, >=, ==, != Relational

The pipe operatormean(my_numbers)

my_numbers %>% mean()

This will be very convenient later on

round(mean(my_numbers))

my_numbers %>% mean() %>% round()

"and then"%>%

R will be FrustratingWe’re going to be adding a lot of objects together.

ggplot(data = mpg, mapping = aes(x = displ, y = hwy)) + geom_point()

"+" goes here

ggplot(data = mpg, mapping = aes(x = displ, y = hwy)) + geom_point()

not here

LET’S GO

library(gapminder) gapminder# A tibble: 1,704 x 6 country continent year lifeExp pop gdpPercap <fctr> <fctr> <int> <dbl> <int> <dbl> 1 Afghanistan Asia 1952 28.801 8425333 779.4453 2 Afghanistan Asia 1957 30.332 9240934 820.8530 3 Afghanistan Asia 1962 31.997 10267083 853.1007 4 Afghanistan Asia 1967 34.020 11537966 836.1971 5 Afghanistan Asia 1972 36.088 13079460 739.9811 6 Afghanistan Asia 1977 38.438 14880372 786.1134 7 Afghanistan Asia 1982 39.854 12881816 978.0114 8 Afghanistan Asia 1987 40.822 13867957 852.3959 9 Afghanistan Asia 1992 41.674 16317921 649.3414 10 Afghanistan Asia 1997 41.763 22227415 635.3414 # ... with 1,694 more rows

p + geom_point()

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp))

p

Named thing gets …

… the output of this function …

… using these arguments

Objects created by ggplot() are unusual in that you can add things to them, and they will work as though you wrote all the code at once.


p + geom_point()

40

60

80

0 30000 60000 90000gdpPercap

lifeExp

Make Some

Graphs

ggplot wants you

to feed it TIDY DATA

gdp lifexp pop continent

340 65 31 Euro

227 51 200 Amer

909 81 80 Euro

126 40 20 Asia

country year cases population 1 Afghanistan 1999 745 19987071 2 Afghanistan 2000 2666 20595360 3 Brazil 1999 37737 172006362 4 Brazil 2000 80488 174504898 5 China 1999 212258 1272915272 6 China 2000 213766 1280428583

country year key value 1 Afghanistan 1999 cases 745 2 Afghanistan 1999 population 19987071 3 Afghanistan 2000 cases 2666 4 Afghanistan 2000 population 20595360 5 Brazil 1999 cases 37737 6 Brazil 1999 population 172006362 7 Brazil 2000 cases 80488 8 Brazil 2000 population 174504898 9 China 1999 cases 212258 10 China 1999 population 1272915272 11 China 2000 cases 213766 12 China 2000 population 1280428583

country year rate 1 Afghanistan 1999 745/19987071 2 Afghanistan 2000 2666/20595360 3 Brazil 1999 37737/172006362 4 Brazil 2000 80488/174504898 5 China 1999 212258/1272915272 6 China 2000 213766/1280428583

country 1999 2000 1 Afghanistan 745 2666 2 Brazil 37737 80488 3 China 212258 213766

country 1999 2000 1 Afghanistan 19987071 20595360 2 Brazil 172006362 174504898 3 China 1272915272 1280428583

GETTING YOUR DATA INTO R

read_dta(file = "data/my_stata_file.dta")

read_spss(file = "data/my_spss_file.sav")

read_sas(data_file = "<NAME>", catalog_file = "<NAME>")

my_data <- read_csv(file = “data/organdonation.csv")

read_csv2(file = "data/my_csv_file.csv")

read_table(file = "<NAME>")

Field delimiter is ;

Field delimiter is ,

Structured but not delimited

url <- "https://cdn.rawgit.com/kjhealy/viz-organdata/master/organdonation.csv"

organs <- read_csv(file = url)

organs <- read_csv(file = "data/organdonation.csv")

Local File Path

Remote URL

engmort <- read_table(file = "data/mortality.txt", skip = 2, na = ".")

HOW ggplot WORKS

ggplot’s FLOW OF ACTION


340 65 31 Euro

227 51 200 Amer

909 81 80 Euro

126 40 20 Asia

AsiaEuroAmer

0-3536-100

>100

log GDP

Life E

xpec

tancy

A Gapminder Plot

Continent

Population


340 65 31 Euro

227 51 200 Amer

909 81 80 Euro

126 40 20 Asia

1. Tidy Data

x=gdp y=lifexp size=pop color=continent

2. Mapping 3. Geomgeom_point()ggplot(mapping = aes(x = …))ggplot(data = gapminder)

x

y y

log10 x

AsiaEuroAmer

0-35

36-100

>100

log GDP

Life E

xpec

tancy

A Gapminder Plot

4. Coordinate System

5. Scales 6. Labels & Guides

Continent

Population

AsiaEuroAmer

0-3536-100

>100

log GDP

Life E

xpec

tancy

A Gapminder Plot

Continent

Population

PIECE BY PIECE

head(gapminder)

## # A tibble: 6 × 6 ## country continent year lifeExp pop gdpPercap ## <fctr> <fctr> <int> <dbl> <int> <dbl> ## 1 Afghanistan Asia 1952 28.801 8425333 779.4453 ## 2 Afghanistan Asia 1957 30.332 9240934 820.8530 ## 3 Afghanistan Asia 1962 31.997 10267083 853.1007 ## 4 Afghanistan Asia 1967 34.020 11537966 836.1971 ## 5 Afghanistan Asia 1972 36.088 13079460 739.9811 ## 6 Afghanistan Asia 1977 38.438 14880372 786.1134

dim(gapminder) ## [1] 1704 6

p <- ggplot(data = gapminder)

Create a ggplot objectData is gapminder table


mapping: tell ggplot the variables you want represented by features of the plot

• The mapping = aes(!!...) instruction links variables to things you will see on the plot.

• The x and y values are the most obvious ones.

• Other aesthetic mappings can include, e.g., color, shape, and size.

Mappings do not directly specify the particular, e.g., colors, shapes, or line styles that will appear on the plot. Rather they establish which variables in the data will be represented by which visible features on the plot.

p + geom_point()

Add a geom layer to the plot

p + geom_smooth()

Try a different geom

This process is literally additive

p + geom_point() + geom_smooth() + scale_x_log10(labels = scales::dollar)

p + geom_point() + geom_smooth(method = "lm")

Every geom is a function. Functions take arguments.

Keep Layering

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp)) p + geom_point() + geom_smooth(method = "lm") + scale_x_log10(label = scales::dollar)

p + geom_point() + geom_smooth(method = "gam") + scale_x_log10(labels = scales::dollar) + labs(x = "GDP Per Capita", y = "Life Expectancy in Years", title = "Economic Growth and Life Expectancy", subtitle = "Data points are country-years", caption = "Data source: Gapminder")

MAPPING vs SETTING

AESTHETICS

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp, color = "purple")) p + geom_point() + geom_smooth(method = "loess") + scale_x_log10()

What has gone wrong here?

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp) p + geom_point(color = "purple") + geom_smooth(method = "loess")) + scale_x_log10()

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp)) p + geom_point(alpha = 0.3) + geom_smooth(color = "orange", se = FALSE, size = 2, method = "lm") + scale_x_log10()

Here, some aesthetics are mapped, and some are set

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp, color = continent, fill = continent)) p + geom_point() + geom_smooth(method = "loess") + scale_x_log10()

MAP or SET AESTHETICS

per geom

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp)) p + geom_point(mapping = aes(color = continent)) + geom_smooth(method = "loess") + scale_x_log10()

PAY CLOSE ATTENTION TO HOW SCALES ARE

DRAWN, AND WHY

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp, color = continent, fill = continent)) p + geom_point() + geom_smooth(method = "loess") + scale_x_log10()

p <- ggplot(data = gapminder, mapping = aes(x = gdpPercap, y = lifeExp)) p + geom_point(mapping = aes(color = continent)) + geom_smooth(method = "loess") + scale_x_log10()

REMEMBER: EVERY MAPPED

VARIABLE HAS A SCALE

Saving Your Work

ggsave()

ggsave("figures/my_figure.png")

ggsave("my_figure.pdf")

ggsave("my_figure.pdf", plot = p5, scale = 1.2)

ggsave("figures/my-figure.pdf", plot = p5, width = 8, height = 5)

With ggsave

pdf(file = "plot.pdf", height = 5in, width = 5in)

print(p4)

dev.off()

With pdf() or other graphics devices

Open device …

… and close when done

```{r my_plot, fig.cap="My Plot", fig.width=9, fig.height=8}

```

Within an Rmd chunk

p + geom_point(mapping = aes(color = continent)) + geom_smooth(method = "loess") + scale_x_log10()

knitr::opts_chunk$set(fig.width=8, fig.height=5)

Set defaults in your first code chunk

Getting Help

GETTING STARTEDsocviz880.co/slides/02_dataviz_s20_getting_started.pdf · eiusmod tempor incididunt...

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