Introduction to ggplot

# Introduction to ggplot
## Dr. Mine Dogucu
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- This specific lecture will not necessarily show you beautiful plots.

- In this lecture we will focus on how ggplot works.

- In the next lecture we will improve the plots that we make.

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center: invisible

__gg__plot is based on __g__rammar of __g__raphics.

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## Data

```r
glimpse(titanic)
```

```
## Rows: 891
## Columns: 6
## $ survived <lgl> FALSE, TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE, TRUE, T…
## $ pclass <chr> "Third", "First", "Third", "First", "Third", "Third", "First…
## $ sex <fct> sex, sex, sex, sex, sex, sex, sex, sex, sex, sex, sex, sex, …
## $ age <dbl> 22, 38, 26, 35, 35, NA, 54, 2, 27, 14, 4, 58, 20, 39, 14, 55…
## $ fare <dbl> 7.2500, 71.2833, 7.9250, 53.1000, 8.0500, 8.4583, 51.8625, 2…
## $ embarked <fct> Southampton, Cherbourg, Southampton, Southampton, Southampto…
```

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class:inverse middle

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If you had the data and had to draw this bar plot by hand, what would you do?

]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-4-1.png)
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- Consider the data frame
- Count number of passengers in each `pclass`
- Put `pclass` on x-axis.
- Put `count` on y-axis.
- Draw the bars.
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-5-1.png)
]

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- Consider the data frame
- ~~Count number of passengers in each `pclass`~~
- Put `pclass` on x-axis.
- ~~Put `count` on y-axis~~.
- Draw the bars.

R will do some of these steps by default. Making a bar plot with another tool might look slightly different.

]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-6-1.png)
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**3 Steps of Making a Basic ggplot**

1.Pick data

2.Map data onto aesthetics

3.Add the geometric layer

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class: middle

### Step 1 - Pick Data

```r
ggplot(data = titanic)
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-8-1.png)

]

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### Step 2 - Map Data to Aesthetics

```r
ggplot(data = titanic,
*      aes(x = pclass))
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-10-1.png)

]

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### Step 3 - Add the Geometric Layer

```r
ggplot(data = titanic,
       aes(x = pclass)) +
* geom_bar()
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-12-1.png)
]
---

.panel[
.panel-name[Plot]
<img src="02b-intro-ggplot_files/figure-html/unnamed-chunk-13-1.png" style="display: block; margin: auto;" />

]

- Create a ggplot using the `titanic` data frame.
- Map the `pclass` to the x-axis. 
- Add a layer of a bar plot.

]

```r
ggplot(data = titanic,
       aes(x = pclass)) +
  geom_bar()
```

]

]
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class:inverse middle

---

```
## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.
```

]

- Create a ggplot using the `titanic` data frame.
- Map the `fare` to the x-axis. 
- Add a layer of a histogram.

]

```r
ggplot(data = titanic,
       aes(x = fare)) +
  geom_histogram() 
```

]

---
class: middle

### Step 1 - Pick Data

```r
ggplot(data = titanic)
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-18-1.png)

]

---

### Step 2 - Map Data to Aesthetics

```r
ggplot(data = titanic,
*      aes(x = fare))
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-20-1.png)

]

---

### Step 3 - Add the Geometric Layer

```r
ggplot(data = titanic,
       aes(x = fare)) +
* geom_histogram()
```
]

```
## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.
```

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-22-1.png)
]

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## What is this warning?

```
## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.
```

---

```r
ggplot(data = titanic,
       aes(x = fare)) +
* geom_histogram(binwidth = 15)
```

---

]

]

]

]

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[There is no "best" number of bins](https://en.wikipedia.org/wiki/Histogram#Number_of_bins_and_width)

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Pick your favorite color(s) from the list at:

[bit.ly/colors-r](https://bit.ly/colors-r)

---

```r
ggplot(data = titanic,
       aes(x = fare)) +
  geom_histogram(binwidth = 15, 
*                color = "white")
```

---

```r
ggplot(data = titanic,
       aes(x = fare)) +
  geom_histogram(binwidth = 15, 
*                fill = "darkred")
```

---

```r
ggplot(data = titanic,
       aes(x = fare)) +
  geom_histogram(binwidth = 15, 
*                color = "white",
*                fill = "darkred")
```

---

---

## Stacked Bar-Plot

```r
ggplot(data = titanic,
       aes(x = pclass, 
*          fill = survived)) +
  geom_bar() 
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-32-1.png)
]

---

## Standardized Bar Plot

```r
ggplot(data = titanic,
       aes(x = pclass, 
           fill = survived)) + 
* geom_bar(position = "fill")
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-34-1.png)
]

---

## Dodged Bar Plot

```r
ggplot(data = titanic,
       aes(x = pclass, 
           fill = survived)) + 
* geom_bar(position = "dodge")
```
]

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-36-1.png)
]

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## New Data

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## New Data

```r
glimpse(penguins)
```

```
## Rows: 344
## Columns: 8
## $ species <fct> Adelie, Adelie, Adelie, Adelie, Adelie, Adelie, Ade…
## $ island <fct> Torgersen, Torgersen, Torgersen, Torgersen, Torgers…
## $ bill_length_mm <dbl> 39.1, 39.5, 40.3, NA, 36.7, 39.3, 38.9, 39.2, 34.1,…
## $ bill_depth_mm <dbl> 18.7, 17.4, 18.0, NA, 19.3, 20.6, 17.8, 19.6, 18.1,…
## $ flipper_length_mm <int> 181, 186, 195, NA, 193, 190, 181, 195, 193, 190, 18…
## $ body_mass_g <int> 3750, 3800, 3250, NA, 3450, 3650, 3625, 4675, 3475,…
## $ sex <fct> male, female, female, NA, female, male, female, mal…
## $ year <int> 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 200…
```

---

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class: middle inverse

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```
## Warning: Removed 2 rows containing non-finite values (stat_ydensity).
```

]

- Create a ggplot using the `penguins` data frame.
- Map the `species` to the x-axis and `bill_length_mm` to the y-axis. 
- Add a layer of a violin plot.

]

```r
ggplot(penguins,
       aes(x = species,
           y = bill_length_mm))  +
  geom_violin()
```

]

---

]

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class: inverse middle

---

```r
ggplot(penguins,
       aes(x = bill_depth_mm,
           y = bill_length_mm))  +
  geom_point()
```

]

```
## Warning: Removed 2 rows containing missing values (geom_point).
```

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-45-1.png)

]

---

---

```r
ggplot(penguins,
       aes(x = bill_depth_mm,
           y = bill_length_mm,
           color = species)) +
  geom_point()
```

]

```
## Warning: Removed 2 rows containing missing values (geom_point).
```

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-47-1.png)

]

---
.left-panel[

```r
ggplot(penguins,
       aes(x = bill_depth_mm,
           y = bill_length_mm,
           shape = species)) +
  geom_point()
```

]

```
## Warning: Removed 2 rows containing missing values (geom_point).
```

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-49-1.png)

]

---

```r
ggplot(penguins,
       aes(x = bill_depth_mm,
           y = bill_length_mm,
           shape = species)) +
  geom_point()
```

]

```
## Warning: Removed 2 rows containing missing values (geom_point).
```

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-51-1.png)

]

---

```r
ggplot(penguins,
       aes(x = bill_depth_mm,
           y = bill_length_mm,
           shape = species,
           color = species)) +
  geom_point()
```

]

```
## Warning: Removed 2 rows containing missing values (geom_point).
```

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-53-1.png)

]

---

```r
ggplot(penguins,
       aes(x = bill_depth_mm,
           y = bill_length_mm,
           shape = species,
           color = species,
           size = body_mass_g)) +
  geom_point()
```

]

```
## Warning: Removed 2 rows containing missing values (geom_point).
```

![](02b-intro-ggplot_files/figure-html/unnamed-chunk-55-1.png)
]

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