Intro to Data Viz

Lecture 3

Dr. Elijah Meyer

Duke University
STA 199 - Fall 2023

2023-09-05

Checklist

– Are you in the GitHub organization?

– Go to our GitHub. This link is also at the bottom of our slides.

– Do you see hw-01 & ae-02? If not, please talk to the in-class / myself.

– Here is a public repo for today if needed: ae-02

– Keeping up with the Prepare link on course website

– Try cloning AE-02! We will also do this together as a class.

Goals for today

– Think about what to do (and not to do) with visualizations

– Understand the fundamentals of ggplot

– Build appropriate visualizations

– More practice with R

Announcements

– HW-1 is out now; due September 11th.

– No lab this week

Question: R-Highlight

– Sometimes you’ll run the code and nothing happens. Check the left-hand of your console: if it’s a +, it means that R doesn’t think you’ve typed a complete expression and it’s waiting for you to finish it.

Warm Up

– What are the variables?

– What patterns / trend can you takeaway from this graph?

How do we make graphs?

The process

mtcars

You want to create a visualization. The first thing we need to do is set up the canvas…

The process

mtcars |>
ggplot()

The process

    mtcars |>
        ggplot(
        aes(
             x = variable.name, y = variable.name)
               )

aes: describe how variables in the data are mapped to your canvas

The process

+ “and”

When working with ggplot functions, we will add to our canvus using +

The process

    mtcars |>
        ggplot(
        aes(
             x = variable.name, y = variable.name)
               ) +
        geom_point()

The process

ae-02

Recreate

Wrap up: Exercises 2.3.1

Recap of AE

– Construct plots with ggplot().

– Layers of ggplots are separated by +s.

– Aesthetic attributes of a geometries (color, size, transparency, etc.) can be mapped to variables in the data or set by the user.

– Use facet_wrap() when faceting (creating small multiples) by one variable and facet_grid() when faceting by two variables.