Mapping data to graphics

# Mapping Data<br>to Graphics

**Session 3**

.light[PMAP 8921: Data Visualization with R<br>
Andrew Young School of Policy Studies<br>
Summer 2023]

]

---

# Plan for today

.box-4.medium.sp-after-half[Data, aesthetics, & the grammar of graphics]

.box-2.medium.sp-after-half[Grammatical layers]

.box-3.medium.sp-after-half[Aesthetics in extra dimensions]

.box-6.medium[Tidy data]

---

name: grammar-of-graphics
class: center middle section-title section-title-4 animated fadeIn

# Data, aesthetics,<br>& the grammar of graphics

---

???

Source: [Wikipedia](https://en.wikipedia.org/wiki/File:National_Museum_in_Poznan_-_Przej%C5%9Bcie_przez_Berezyn%C4%99.JPG)

---

---

# Long distance!

.center[
<figure>
  <img src="img/03/napoleon-google-maps.png" alt="Moscow to Vilnius" title="Moscow to Vilnius" width="80%">
  <figcaption>Moscow to Vilnius</figcaption>
</figure>
]

---

# Very cold!

---

# Lots of people died!

---

???

Source: [Wikimedia Commons](https://upload.wikimedia.org/wikipedia/commons/2/29/Minard.png)

---

---

# Mapping data to aesthetics

.pull-left.center[

]

.box-inv-4.medium[Aesthetic]

.box-4.sp-after[Position, shape, color, etc.]

.box-inv-4.medium[Data]

]

---

# Mapping data to aesthetics

<table>
  <tr>
    <th class="cell-left">Data</th>
    <th class="cell-left">Aesthetic</th>
    <th class="cell-left">Graphic/Geometry</th>
  </tr>
  <tr>
    <td class="cell-left">Longitude</td>
    <td class="cell-left">Position (x-axis)&emsp;</td>
    <td class="cell-left">Point</td>
  </tr>
  <tr>
    <td class="cell-left">Latitude</td>
    <td class="cell-left">Position (y-axis)</td>
    <td class="cell-left">Point</td>
  </tr>
  <tr>
    <td class="cell-left">Army size</td>
    <td class="cell-left">Size</td>
    <td class="cell-left">Path</td>
  </tr>
  <tr>
    <td class="cell-left">Army direction&emsp;</td>
    <td class="cell-left">Color</td>
    <td class="cell-left">Path</td>
  </tr>
  <tr>
    <td class="cell-left">Date</td>
    <td class="cell-left">Position (x-axis)</td>
    <td class="cell-left">Line + text</td>
  </tr>
  <tr>
    <td class="cell-left">Temperature</td>
    <td class="cell-left">Position (y-axis)</td>
    <td class="cell-left">Line + text</td>
  </tr>
</table>

---

# Mapping data to aesthetics

<table>
  <tr>
    <th class="cell-left">Data</th>
    <th class="cell-left"><code class="remark-inline-code">aes()</code></th>
    <th class="cell-left"><code class="remark-inline-code">geom</code></th>
  </tr>
  <tr>
    <td class="cell-left">Longitude</td>
    <td class="cell-left"><code class="remark-inline-code">x</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_point()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Latitude</td>
    <td class="cell-left"><code class="remark-inline-code">y</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_point()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Army size</td>
    <td class="cell-left"><code class="remark-inline-code">size</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_path()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Army direction&emsp;</td>
    <td class="cell-left"><code class="remark-inline-code">color</code>&emsp;</td>
    <td class="cell-left"><code class="remark-inline-code">geom_path()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Date</td>
    <td class="cell-left"><code class="remark-inline-code">x</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_line() + geom_text()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Temperature</td>
    <td class="cell-left"><code class="remark-inline-code">y</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_line() + geom_text()</code></td>
  </tr>
</table>

---

# `ggplot()` template

<code class ='r hljs remark-code'>ggplot(data = <b><span style="background-color:#CBB5FF">DATA</span></b>) +<br>&nbsp;&nbsp;<b><span style="background-color:#FFDFD1">GEOM_FUNCTION</span></b>(mapping = aes(<b><span style="background-color:#FFD0CF">AESTHETIC MAPPINGS</span></b>))</code>

<code class ='r hljs remark-code'>ggplot(data = <b><span style="background-color:#CBB5FF">troops</span></b>) +<br>&nbsp;&nbsp;<b><span style="background-color:#FFDFD1">geom_path</span></b>(mapping = aes(<b><span style="background-color:#FFD0CF">x = longitude</span></b>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<b><span style="background-color:#FFD0CF">y = latitude</span></b>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<b><span style="background-color:#FFD0CF">color = direction</span></b>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<b><span style="background-color:#FFD0CF">size = survivors</span></b>))</code>

---

<table>
 <thead>
  <tr>
   <th style="text-align:left;"> longitude </th>
   <th style="text-align:left;"> latitude </th>
   <th style="text-align:left;"> direction </th>
   <th style="text-align:left;"> survivors </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:left;"> 24 </td>
   <td style="text-align:left;"> 54.9 </td>
   <td style="text-align:left;"> A </td>
   <td style="text-align:left;"> 340000 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 24.5 </td>
   <td style="text-align:left;"> 55 </td>
   <td style="text-align:left;"> A </td>
   <td style="text-align:left;"> 340000 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> … </td>
   <td style="text-align:left;"> … </td>
   <td style="text-align:left;"> … </td>
   <td style="text-align:left;"> … </td>
  </tr>
</tbody>
</table>

]

---

---

???

Source: [New York Times](https://www.nytimes.com/2017/02/09/world/europe/hans-rosling-dead-statistician.html)

---

???

Source: [Gapminder](https://www.gapminder.org/tools/#$chart-type=bubbles)

---

---

# Mapping data to aesthetics

<table>
  <tr>
    <th class="cell-left">Data</th>
    <th class="cell-left"><code class="remark-inline-code">aes()</code></th>
    <th class="cell-left"><code class="remark-inline-code">geom</code></th>
  </tr>
  <tr>
    <td class="cell-left">Wealth (GDP/capita)</td>
    <td class="cell-left"><code class="remark-inline-code">x</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_point()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Health (Life expectancy)&emsp;</td>
    <td class="cell-left"><code class="remark-inline-code">y</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_point()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Continent</td>
    <td class="cell-left"><code class="remark-inline-code">color</code></td>
    <td class="cell-left"><code class="remark-inline-code">geom_point()</code></td>
  </tr>
  <tr>
    <td class="cell-left">Population</td>
    <td class="cell-left"><code class="remark-inline-code">size</code>&emsp;</td>
    <td class="cell-left"><code class="remark-inline-code">geom_point()</code></td>
  </tr>
</table>

---

<table>
 <thead>
  <tr>
   <th style="text-align:center;"> country </th>
   <th style="text-align:center;"> continent </th>
   <th style="text-align:center;"> gdpPercap </th>
   <th style="text-align:center;"> lifeExp </th>
   <th style="text-align:center;"> pop </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:center;"> Afghanistan </td>
   <td style="text-align:center;"> Asia </td>
   <td style="text-align:center;"> 974.5803384 </td>
   <td style="text-align:center;"> 43.828 </td>
   <td style="text-align:center;"> 31889923 </td>
  </tr>
  <tr>
   <td style="text-align:center;"> Albania </td>
   <td style="text-align:center;"> Europe </td>
   <td style="text-align:center;"> 5937.029526 </td>
   <td style="text-align:center;"> 76.423 </td>
   <td style="text-align:center;"> 3600523 </td>
  </tr>
  <tr>
   <td style="text-align:center;"> … </td>
   <td style="text-align:center;"> … </td>
   <td style="text-align:center;"> … </td>
   <td style="text-align:center;"> … </td>
   <td style="text-align:center;"> … </td>
  </tr>
</tbody>
</table>

]

<code class ='r hljs remark-code'>ggplot(data = <b><span style="background-color:#CBB5FF">gapminder_2007</span></b>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;mapping = aes(<b><span style="background-color:#FFD0CF">x = gdpPercap</span></b>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<b><span style="background-color:#FFD0CF">y = lifeExp</span></b>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<b><span style="background-color:#FFD0CF">color = continent</span></b>,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<b><span style="background-color:#FFD0CF">size = pop</span></b>)) +<br>&nbsp;&nbsp;<b><span style="background-color:#FFDFD1">geom_point</span></b>() +<br>&nbsp;&nbsp;scale_x_log10()</code>

---

---

# Health and wealth

---

layout: false
name: grammatical-layers
class: center middle section-title section-title-2 animated fadeIn

# Grammatical layers

---

---

# Grammar components as layers

&nbsp;

![](img/03/ggplot-layers-short@4x.png)
]

???

Layer analogy borrowed from [Thomas Lin Pedersen](https://www.data-imaginist.com/) and his ["Drawing Anything with ggplot2" workshop](https://github.com/thomasp85/ggplot2_workshop).

---

# Possible aesthetics

.box-inv-2.small[`color` (discrete)]

.box-inv-2.small[`color` (continuous)]

<img src="03-slides_files/figure-html/aes-color-continuous-1.png" width="100%" style="display: block; margin: auto;" />
]

.box-inv-2.small[`size`]

.box-inv-2.small[`fill`]

<img src="03-slides_files/figure-html/aes-fill-1.png" width="100%" style="display: block; margin: auto;" />
]

.box-inv-2.small[`shape`]

.box-inv-2.small[`alpha`]

<img src="03-slides_files/figure-html/aes-alpha-1.png" width="100%" style="display: block; margin: auto;" />
]

---

# Possible geoms

<table>
  <tr>
    <th class="cell-left"></th>
    <th class="cell-left">Example geom</th>
    <th class="cell-left">What it makes</th>
  </tr>
  <tr>
    <td class="cell-left"><img src="img/03/geom_bar.png"></td>
    <td class="cell-left"><code class="remark-inline-code">geom_col()</code></td>
    <td class="cell-left">Bar charts</td>
  </tr>
  <tr>
    <td class="cell-left"><img src="img/03/geom_text.png"></td>
    <td class="cell-left"><code class="remark-inline-code">geom_text()</code></td>
    <td class="cell-left">Text</td>
  </tr>
  <tr>
    <td class="cell-left"><img src="img/03/geom_point.png"></td>
    <td class="cell-left"><code class="remark-inline-code">geom_point()</code></td>
    <td class="cell-left">Points</td>
  </tr>
  <tr>
    <td class="cell-left"><img src="img/03/geom_boxplot.png"></td>
    <td class="cell-left"><code class="remark-inline-code">geom_boxplot()</code>&emsp;</td>
    <td class="cell-left">Boxplots</td>
  </tr>
  <tr>
    <td class="cell-left"><img src="img/03/geom_sf.png"></td>
    <td class="cell-left"><code class="remark-inline-code">geom_sf()</code></td>
    <td class="cell-left">Maps</td>
  </tr>
</table>

---

# Possible geoms

.box-2[See [the {ggplot2} documentation](https://ggplot2.tidyverse.org/reference/index.html#section-layer-geoms) for<br>complete examples of all the different geom layers]

---

# Additional layers

.box-inv-2[We sequentially add layers onto the foundational `ggplot()` plot to create complex figures]
]

---

# Scales

<table>
  <tr>
    <th class="cell-left">Example layer</th>
    <th class="cell-left">What it does</th>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">scale_x_continuous()</code></td>
    <td class="cell-left">Make the x-axis continuous</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">scale_x_continuous(breaks = 1:5)&ensp;</code></td>
    <td class="cell-left">Manually specify axis ticks</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">scale_x_log10()</code></td>
    <td class="cell-left">Log the x-axis</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">scale_color_gradient()</code></td>
    <td class="cell-left">Use a gradient</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">scale_fill_viridis_d()</code></td>
    <td class="cell-left">Fill with discrete viridis colors</td>
  </tr>
</table>

---

# Scales

.box-inv-2.small[`scale_x_log10()`]

<img src="03-slides_files/figure-html/scale-example-1-1.png" width="100%" style="display: block; margin: auto;" />
]

.box-inv-2.small[`scale_color_viridis_d()`]

<img src="03-slides_files/figure-html/scale-example-2-1.png" width="100%" style="display: block; margin: auto;" />
]

---

# Facets

<table>
  <tr>
    <th class="cell-left">Example layer</th>
    <th class="cell-left">What it does</th>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">facet_wrap(vars(continent))</code></td>
    <td class="cell-left">Plot for each continent</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">facet_wrap(vars(continent, year))</code>&emsp;</td>
    <td class="cell-left">Plot for each continent/year</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">facet_wrap(..., ncol = 1)</code></td>
    <td class="cell-left">Put all facets in one column</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">facet_wrap(..., nrow = 1)</code></td>
    <td class="cell-left">Put all facets in one row</td>
  </tr>
</table>

---

# Facets

.box-inv-2.small[`facet_wrap(vars(continent))`]

<img src="03-slides_files/figure-html/facet-example-1-1.png" width="100%" style="display: block; margin: auto;" />
]

.box-inv-2.small[`facet_wrap(vars(continent, year))`]

<img src="03-slides_files/figure-html/facet-example-2-1.png" width="100%" style="display: block; margin: auto;" />
]

---

# Coordinates

<table>
  <tr>
    <th class="cell-left">Example layer</th>
    <th class="cell-left">What it does</th>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">coord_cartesian()</code></td>
    <td class="cell-left">Plot for each continent</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">coord_cartesian(ylim = c(1, 10))</code>&emsp;</td>
    <td class="cell-left">Zoom in where y is 1–10</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">coord_flip()</code></td>
    <td class="cell-left">Switch x and y</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">coord_polar()</code></td>
    <td class="cell-left">Use circular polar system</td>
  </tr>
</table>

---

# Coordinates

.box-inv-2.small[`coord_cartesian(ylim = c(70, 80), xlim = c(10000, 30000))`]

<img src="03-slides_files/figure-html/coord-example-1-1.png" width="100%" style="display: block; margin: auto;" />
]

.box-inv-2.small[`coord_flip()`]

<img src="03-slides_files/figure-html/coord-example-2-1.png" width="100%" style="display: block; margin: auto;" />
]

---

# Labels

<table>
  <tr>
    <th class="cell-left">Example layer</th>
    <th class="cell-left">What it does</th>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">labs(title = "Neat title")</code></td>
    <td class="cell-left">Title</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">labs(caption = "Something")</td>
    <td class="cell-left">Caption</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">labs(y = "Something")</td>
    <td class="cell-left">y-axis</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">labs(size = "Population")</code></td>
    <td class="cell-left">Title of size legend</td>
  </tr>
</table>

---

# Labels

```r
ggplot(gapminder_2007, 
       aes(x = gdpPercap, y = lifeExp, 
           color = continent, size = pop)) +
  geom_point() +
  scale_x_log10() +
  labs(title = "Health and wealth grow together",
       subtitle = "Data from 2007",
       x = "Wealth (GDP per capita)",
       y = "Health (life expectancy)",
       color = "Continent",
       size = "Population",
       caption = "Source: The Gapminder Project")
```
]

---

# Theme

<table>
  <tr>
    <th class="cell-left">Example layer</th>
    <th class="cell-left">What it does</th>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">theme_grey()</code></td>
    <td class="cell-left">Default grey background</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">theme_bw()</td>
    <td class="cell-left">Black and white</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">theme_dark()</td>
    <td class="cell-left">Dark</td>
  </tr>
  <tr>
    <td class="cell-left"><code class="remark-inline-code">theme_minimal()</code></td>
    <td class="cell-left">Minimal</td>
  </tr>
</table>

---

# Theme

.box-inv-2.small[`theme_dark()`]

<img src="03-slides_files/figure-html/theme-example-1-1.png" width="100%" style="display: block; margin: auto;" />
]

.box-inv-2.small[`theme_minimal()`]

<img src="03-slides_files/figure-html/theme-example-2-1.png" width="100%" style="display: block; margin: auto;" />
]

---

# Theme

.box-inv-2[There are collections of pre-built themes online,<br>like [the {ggthemes} package](https://jrnold.github.io/ggthemes/)]

.center[
<figure>
  <img src="img/03/ggthemes.png" alt="ggthemes" title="ggthemes" width="45%">
</figure>
]

---

# Theme

.box-inv-2[Organizations often make their own custom themes, [like the BBC](https://bbc.github.io/rcookbook/)]

.center[
<figure>
  <img src="img/03/bbc-cookbook.png" alt="ggthemes" title="ggthemes" width="80%">
</figure>
]

---

# Theme options

```r
theme_bw() + 
theme(legend.position = "bottom",
      plot.title = element_text(face = "bold"),
      panel.grid = element_blank(),
      axis.title.y = element_text(face = "italic"))
```

---

# So many possibilities!

.box-2[See [the {ggplot2} documentation](https://ggplot2.tidyverse.org/reference/index.html) for<br>complete examples of everything you can do]
]

---

# Putting it all together

.box-inv-2.medium[We can build a plot sequentially<br>to see how each grammatical layer<br>changes the appearance]

---

```r
*ggplot(data = mpg,
*      mapping = aes(x = displ,
*                    y = hwy,
*                    color = drv))
```
]

---

```r
ggplot(data = mpg,
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
* geom_point()
```
]

---

```r
ggplot(data = mpg,
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
* geom_smooth()
```
]

---

```r
ggplot(data = mpg,
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
* geom_smooth(method = "lm")
```
]

---

```r
ggplot(data = mpg,
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
  geom_smooth(method = "lm") +
* scale_color_viridis_d()
```
]

---

```r
ggplot(data = mpg,
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
  geom_smooth(method = "lm") +
  scale_color_viridis_d() +
* facet_wrap(vars(drv), ncol = 1)
```
]

---

```r
ggplot(data = mpg,
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
  geom_smooth(method = "lm") +
  scale_color_viridis_d() +
  facet_wrap(vars(drv), ncol = 1) +
* labs(x = "Displacement", y = "Highway MPG",
*      color = "Drive",
*      title = "Heavier cars get lower mileage",
*      subtitle = "Displacement indicates weight(?)",
*      caption = "I know nothing about cars")
```
]

---

```r
ggplot(data = mpg,
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
  geom_smooth(method = "lm") +
  scale_color_viridis_d() +
  facet_wrap(vars(drv), ncol = 1) +
  labs(x = "Displacement", y = "Highway MPG",
       color = "Drive", 
       title = "Heavier cars get lower mileage",
       subtitle = "Displacement indicates weight(?)",
       caption = "I know nothing about cars") +
* theme_bw()
```
]

---

```r
ggplot(data = mpg, 
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
  geom_smooth(method = "lm") +
  scale_color_viridis_d() +
  facet_wrap(vars(drv), ncol = 1) +
  labs(x = "Displacement", y = "Highway MPG",
       color = "Drive", 
       title = "Heavier cars get lower mileage",
       subtitle = "Displacement indicates weight(?)",
       caption = "I know nothing about cars") +
  theme_bw() +
* theme(legend.position = "bottom",
*       plot.title = element_text(face = "bold"))
```
]

---

```r
ggplot(data = mpg, 
       mapping = aes(x = displ,
                     y = hwy,
                     color = drv)) +
  geom_point() +
  geom_smooth(method = "lm") + 
  scale_color_viridis_d() +
  facet_wrap(vars(drv), ncol = 1) +
  labs(x = "Displacement", y = "Highway MPG",
       color = "Drive", 
       title = "Heavier cars get lower mileage",
       subtitle = "Displacement indicates weight(?)",
       caption = "I know nothing about cars") +
  theme_bw() +
  theme(legend.position = "bottom",
        plot.title = element_text(face = "bold"))
```
]

---

---

# A true grammar

.box-2.small[Hunt through Excel menus for a stacked bar chart and manually reshape your data to work with it]
]

.pull-right[
.center[
<figure>
  <img src="img/03/excel-chart-types.png" alt="Excel chart types" title="Excel chart types" width="78%">
</figure>
]
]

---

# A true grammar

.box-2.small[Map a column to the x-axis, fill by a different variable, and `geom_col()` to get stacked bars]

.box-2.small[Geoms can be interchangable<br>(e.g. switch `geom_violin()` to `geom_boxplot()`)]
]

.pull-right[
.center[
<figure>
  <img src="img/03/ggplot-layers@4x.png" alt="Grammar of graphics layers" title="Grammar of graphics layers" width="100%">
</figure>
]
]

---

# Describing graphs with the grammar

.left-code[
.box-2.small[Map wealth to the x-axis, health to the y-axis, add points, color by continent, size by population, scale the y-axis with a log, and facet by year]

```r
ggplot(data = filter(gapminder, year %in% c(2002, 2007)), 
       mapping = aes(x = gdpPercap,
                     y = lifeExp,
                     color = continent,
                     size = pop)) +
  geom_point() +
  scale_x_log10() + 
  facet_wrap(vars(year), ncol = 1)
```
]

---

# Describing graphs with the grammar

.left-code[
.box-2.small[Map health to the x-axis, add a histogram with bins for every 5 years, fill and facet by continent]

```r
ggplot(data = gapminder_2007, 
       mapping = aes(x = lifeExp,
                     fill = continent)) +
  geom_histogram(binwidth = 5, 
                 color = "white") +
  guides(fill = "none") +  # Turn off legend
  facet_wrap(vars(continent))
```
]

---

# Describing graphs with the grammar

.left-code[
.box-2.small[Map continent to the x-axis, health to the y-axis, add violin plots and semi-transparent boxplots, fill by continent]

```r
ggplot(data = gapminder, 
       mapping = aes(x = continent,
                     y = lifeExp,
                     fill = continent)) +
  geom_violin() +
  geom_boxplot(alpha = 0.5) +
  guides(fill = "none")  # Turn off legend
```
]

---

layout: false
name: extra-dimensions
class: center middle section-title section-title-3 animated fadeIn

# Aesthetics in<br>extra dimensions

---

---

# Time

```r
ggplot(gapminder, aes(x = gdpPercap, y = lifeExp, 
                      size = pop, color = country)) +
  geom_point(alpha = 0.7) +
  scale_size(range = c(2, 12)) +
  scale_x_log10(labels = scales::dollar) +
  guides(size = "none", color = "none") +
  facet_wrap(~continent) +
  # Special gganimate stuff
  labs(title = 'Year: {frame_time}', x = 'GDP per capita', y = 'life expectancy') +
  transition_time(year) +
  ease_aes('linear')
```
]

---

# Sound

.box-3.small[<http://graphics.wsj.com/hamilton/>]

.center[
<figure>
  <img src="img/03/hamilton.png" alt="Daveed Diggs in 'Washington On Your Side'" title="Daveed Diggs in 'Washington On Your Side'" width="60%">
</figure>
]

---

.center[
<figure>
  <img src="img/03/hamilton-1.png" alt="Daveed Diggs in 'Washington On Your Side'" title="Daveed Diggs in 'Washington On Your Side'" width="75%">
</figure>

<figure>
  <img src="img/03/hamilton-2.png" alt="Kendrick Lamar in 'good kid, m.A.A.d city'" title="Kendrick Lamar in 'good kid, m.A.A.d city'" width="75%">
</figure>
]

---

---

# Animation, time, and sound

.center[
<iframe width="800" height="450" src="https://www.youtube.com/embed/__Jgp18tCnE" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
]

???

Erika Navarro for the Weather Channel: <https://www.pewtrusts.org/en/research-and-analysis/articles/2018/12/03/the-weather-channel-uses-animation-to-show-dangers-of-storm-surge>

---

layout: false
name: tidy-data
class: center middle section-title section-title-6 animated fadeIn

# Tidy data

---

---

# Data shapes

.box-inv-6.medium[For `ggplot()` to work,<br>your data needs to be in a **tidy** format]

---

# Tidy data

.center[
<figure>
  <img src="img/03/tidy-1.png" alt="Tidy data" title="Tidy data" width="70%">
  <figcaption><a href="https://r4ds.had.co.nz/tidy-data.html">From chapter 12 of <em>R for Data Science</em></a></figcaption>
</figure>
]

---

# Untidy data example

.center[
<figure>
  <img src="img/03/untidy-example.png" alt="Example of untidy data" title="Example of untidy data" width="60%">
</figure>
]

---

# Tidy data example

.center[
<figure>
  <img src="img/03/tidy-example.png" alt="Example of tidy data" title="Example of tidy data" width="50%">
</figure>
]

---

# Wide vs. long

.center[
<figure>
  <img src="img/03/original-dfs-tidy.png" alt="Example of tidy data" title="Example of tidy data" width="50%">
</figure>
]

???

Figure by Garrick Aden-Buie in [{tidyexplain}](https://github.com/gadenbuie/tidyexplain)

---

# Moving from wide to long

.box-inv-6.tiny[Nowadays, `gather()` is called `pivot_longer()` and `spread()` is called `pivot_wider()`]

.center[
<img src="img/03/tidyr-spread-gather.gif" alt="Moving from wide to long" title="Moving from wide to long" width="35%">
]

???

Figure by Garrick Aden-Buie in [{tidyexplain}](https://github.com/gadenbuie/tidyexplain)