Visualization - Aesthetic Mapping

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.title[
# Visualization - Aesthetic Mapping
]

---

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---
# A visualization:

- is a geometry object (a geom)

- whose aesthetics

- represents variables

- from a data set

---
# Aesthetics mean

- “something you can see”.

Examples include:

- position (i.e., on the x and y axes)
- color (“outside” color)
- fill (“inside” color)
- shape (of points)
- size

---
# Aesthetics Mapping

- map

- variables

- to aesthetics

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# Examples

---

```r
library(tidyverse)
library(knitr)    # For knitting document and include_graphics function
df <- read_csv('https://bryantstats.github.io/math421/data/all-states-history.csv')
library(lubridate)

df <- df %>% 
    filter(positiveIncrease>0) %>% 
    mutate(year = year(date),
           quarters = quarters(date),
           month = month(date),
           day = wday(date),
           day_type = case_when(day < 6 ~ 'weekday',
                                TRUE~'weekend'))
```

---

```r
df %>% filter(state=='RI'|state=='MA') %>% ggplot()+
  geom_point(mapping = aes(x = date, 
                           y = positiveIncrease, 
                           color = state))
```

![](6_viz_files/figure-html/unnamed-chunk-3-1.png)

---

```r
df %>% filter(state=='RI'|state=='MA') %>% ggplot()+
  geom_line(mapping = aes(x = date, 
                          y = positiveIncrease, 
                          color = state))
```

![](6_viz_files/figure-html/unnamed-chunk-4-1.png)

---

```r
df %>% ggplot()+
  geom_smooth(mapping = aes(x = positiveIncrease, 
                            y = deathIncrease, 
                            color = day_type))
```

![](6_viz_files/figure-html/unnamed-chunk-5-1.png)

---

```r
df %>% filter(month >8, year==2020) %>% ggplot()+
  geom_smooth(mapping = aes(x = positiveIncrease, 
                            y = deathIncrease, 
                            color = day_type))
```

![](6_viz_files/figure-html/unnamed-chunk-6-1.png)

---

```r
df %>% filter(state=='RI'|state=='MA') %>% ggplot()+
  geom_density(mapping = aes(x = positiveIncrease, 
                             color = state))
```

![](6_viz_files/figure-html/unnamed-chunk-7-1.png)
---

```r
df %>% filter(state=='RI'|state=='MA') %>% ggplot()+
  geom_bar(mapping = aes(x = day_type, 
                         fill = state))
```

![](6_viz_files/figure-html/unnamed-chunk-8-1.png)
---
# Aesthetic of a geom

- A geom has its list of own aesthetics

- Use `?geom_point()` to check for the list of `geom_point`

- Some aesthetics are required, some are not

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# Required Aesthetics

---

```r
df %>% filter(state=='RI'|state=='MA') %>% ggplot()+
  geom_point(mapping = aes(x = date, 
                           y = positiveIncrease, 
                           color = state))
```

![](6_viz_files/figure-html/unnamed-chunk-9-1.png)
---

```r
df %>% filter(state=='RI'|state=='MA') %>% ggplot()+
  geom_point(mapping = aes(x = date, y = positiveIncrease))
```

![](6_viz_files/figure-html/unnamed-chunk-10-1.png)

---

```r
df %>% filter(state=='RI'|state=='MA') %>% ggplot()+
  geom_point(mapping = aes(x = date))
```

- Will produce an error since `y` aesthetic is required for `geom_point`.

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# Common Visualization Practices

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# One Continuous Variable

- Density: `geom_density`

- Histogram: `geom_histogram`

- Boxplot: `geom_boxplot`

---
**One Continuous Variable: Density**

```r
df %>% ggplot()+
  geom_density(mapping = aes(x = positiveIncrease))
```

![](6_viz_files/figure-html/unnamed-chunk-12-1.png)

---
**One Continuous Variable: Histogram**

```r
df %>% ggplot()+
  geom_histogram(mapping = aes(x = positiveIncrease))
```

![](6_viz_files/figure-html/unnamed-chunk-13-1.png)
---
**One Continuous Variable: Boxplot**

```r
df %>% ggplot()+
  geom_boxplot(mapping = aes(y = positiveIncrease))
```

![](6_viz_files/figure-html/unnamed-chunk-14-1.png)
---
**One Continuous Variable: Boxplot**

```r
df %>% filter(positiveIncrease<1000) %>% ggplot()+
  geom_boxplot(mapping = aes(y = positiveIncrease))
```

![](6_viz_files/figure-html/unnamed-chunk-15-1.png)
---
**One Categorical Variable: Bar chart**

```r
df %>% ggplot()+
  geom_bar(mapping = aes(x = day_type))
```

![](6_viz_files/figure-html/unnamed-chunk-16-1.png)

---
# Two Continuous Variables

- Scatter Plot: `geom_point`
- Line Plot: `geom_line`
- Smooth Plot: `geom_smooth`

---
# One Continuous Variable + One Categorical Variable

- Density
- BoxPlot

---
**One Continuous + One Categorical: Density**

```r
df %>% ggplot()+
  geom_density(mapping = aes(x = positiveIncrease, color = day_type))
```

![](6_viz_files/figure-html/unnamed-chunk-17-1.png)

---
**One Continuous + One Categorical: Density**

```r
df %>% filter(positiveIncrease<1000) %>% ggplot()+
  geom_density(mapping = aes(x = positiveIncrease, color = day_type))
```

![](6_viz_files/figure-html/unnamed-chunk-18-1.png)

---
**One Continuous + One Categorical: Boxplot**

```r
df %>% ggplot()+
  geom_boxplot(mapping = aes(x = positiveIncrease, y = day_type))
```

![](6_viz_files/figure-html/unnamed-chunk-19-1.png)
---
**One Continuous + One Categorical: Boxplot**

```r
df %>% filter(positiveIncrease<1000) %>% ggplot()+
  geom_boxplot(mapping = aes(x = positiveIncrease, y = day_type))
```

![](6_viz_files/figure-html/unnamed-chunk-20-1.png)
---
# One Categorical Variable + One Categorical Variable

- Barplot

---
**One Categorical + One Categorical: Barplot**

```r
df %>% ggplot()+
  geom_bar(mapping=aes(x=month, fill=day_type), position='dodge')
```

![](6_viz_files/figure-html/unnamed-chunk-21-1.png)
---
# More

- [ggplot cheat sheet](https://raw.githubusercontent.com/rstudio/cheatsheets/main/data-visualization.pdf), or [backup](data-visualization.pdf)