Tidy Data

#Tidy data#

L. Paloma Rojas Saunero

---

---

```r
library(tidyr)
```

---

## The rules of Tidy data:

- **Rule 1**: Each **_variable_** must have its own **_column_**.
<br><br><br><br><br><br>
- **Rule 2**: Each **_observation_** must have its own **_row_**.
<br><br><br><br><br><br>
- **Rule 3**: Each **_value_** must have its own **_cell_**.
]

<center>
![rule](figs/rules.png)
<center>
]
.foot-note[https://r4ds.had.co.nz/]
---
### Quiz 1

Which of these tables meets the 3 rules of tidy data?

.pull-left[
**Table A**
<table class="table table-hover table-condensed table-responsive" style="font-size: 14px; width: auto !important; margin-left: auto; margin-right: auto;">
 <thead>
  <tr>
   <th style="text-align:left;"> country </th>
   <th style="text-align:right;"> 1999 </th>
   <th style="text-align:right;"> 2000 </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:left;"> Afghanistan </td>
   <td style="text-align:right;"> 745 </td>
   <td style="text-align:right;"> 2666 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> Brazil </td>
   <td style="text-align:right;"> 37737 </td>
   <td style="text-align:right;"> 80488 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> China </td>
   <td style="text-align:right;"> 212258 </td>
   <td style="text-align:right;"> 213766 </td>
  </tr>
</tbody>
</table>

**Table B**
<table class="table table-hover table-condensed table-responsive" style="font-size: 14px; width: auto !important; margin-left: auto; margin-right: auto;">
 <thead>
  <tr>
   <th style="text-align:left;"> country </th>
   <th style="text-align:right;"> year </th>
   <th style="text-align:left;"> rate </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:left;"> Afghanistan </td>
   <td style="text-align:right;"> 1999 </td>
   <td style="text-align:left;"> 745/19987071 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> Afghanistan </td>
   <td style="text-align:right;"> 2000 </td>
   <td style="text-align:left;"> 2666/20595360 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> Brazil </td>
   <td style="text-align:right;"> 1999 </td>
   <td style="text-align:left;"> 37737/172006362 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> Brazil </td>
   <td style="text-align:right;"> 2000 </td>
   <td style="text-align:left;"> 80488/174504898 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> China </td>
   <td style="text-align:right;"> 1999 </td>
   <td style="text-align:left;"> 212258/1272915272 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> China </td>
   <td style="text-align:right;"> 2000 </td>
   <td style="text-align:left;"> 213766/1280428583 </td>
  </tr>
</tbody>
</table>

]

<table class="table table-hover table-condensed table-responsive" style="font-size: 14px; width: auto !important; margin-left: auto; margin-right: auto;">
 <thead>
  <tr>
   <th style="text-align:left;"> country </th>
   <th style="text-align:right;"> year </th>
   <th style="text-align:right;"> cases </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:left;"> Afghanistan </td>
   <td style="text-align:right;"> 1999 </td>
   <td style="text-align:right;"> 745 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> Afghanistan </td>
   <td style="text-align:right;"> 2000 </td>
   <td style="text-align:right;"> 2666 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> Brazil </td>
   <td style="text-align:right;"> 1999 </td>
   <td style="text-align:right;"> 37737 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> Brazil </td>
   <td style="text-align:right;"> 2000 </td>
   <td style="text-align:right;"> 80488 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> China </td>
   <td style="text-align:right;"> 1999 </td>
   <td style="text-align:right;"> 212258 </td>
  </tr>
  <tr>
   <td style="text-align:left;"> China </td>
   <td style="text-align:right;"> 2000 </td>
   <td style="text-align:right;"> 213766 </td>
  </tr>
</tbody>
</table>

]
---
## Reshape: Wide to long _(cols to rows)_

![w2l](figs/w2l_full.png)

---

## `pivot_longer()`

![w2l_1](figs/w2l_step1.png)
]

```r
pivot_longer( 
* cols = c(`1991`, `2000`),
* names_to = "year",
  values_to = "cases")
```
]

---

## `pivot_longer()`

![w2l_2](figs/w2l_step2.png)
]

```r
pivot_longer( 
  cols,
  names_to = "year",
* values_to = "cases")
```
]

---

## Reshape: Long to wide _(rows to cols)_

![l2w](figs/l2w_full.png)

---

## `pivot_wider()`

![l2w_1](figs/l2w_step1.png)]

```r
pivot_wider(
* names_from = year,
  values_from = cases)
```
]

---

## `pivot_wider()`

![l2w_1](figs/l2w_step2.png)]

```r
pivot_wider(
  names_from = year,
* values_from = cases)
```
]

---
### Quiz 2

We need to reshape the tibble that looks like table 1 to look as table 2. Fill in the blanks, correct if necessary:

```r
table %>% 
  pivot_____(names_from = "____",
              values_from = "____")
```

.pull-left[
**Table 1**
<table class="table table-hover table-condensed table-responsive" style="font-size: 14px; width: auto !important; margin-left: auto; margin-right: auto;">
 <thead>
  <tr>
   <th style="text-align:right;"> student </th>
   <th style="text-align:left;"> food </th>
   <th style="text-align:right;"> rate </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:right;"> 1 </td>
   <td style="text-align:left;"> fruit </td>
   <td style="text-align:right;"> 3 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 1 </td>
   <td style="text-align:left;"> vegetable </td>
   <td style="text-align:right;"> 5 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 1 </td>
   <td style="text-align:left;"> icecream </td>
   <td style="text-align:right;"> 7 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 2 </td>
   <td style="text-align:left;"> fruit </td>
   <td style="text-align:right;"> 4 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 2 </td>
   <td style="text-align:left;"> vegetable </td>
   <td style="text-align:right;"> 8 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 2 </td>
   <td style="text-align:left;"> icecream </td>
   <td style="text-align:right;"> 5 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 3 </td>
   <td style="text-align:left;"> fruit </td>
   <td style="text-align:right;"> 1 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 3 </td>
   <td style="text-align:left;"> vegetable </td>
   <td style="text-align:right;"> 4 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 3 </td>
   <td style="text-align:left;"> icecream </td>
   <td style="text-align:right;"> 4 </td>
  </tr>
</tbody>
</table>
]
.pull-right[
**Table 2**
<table class="table table-hover table-condensed table-responsive" style="font-size: 14px; width: auto !important; margin-left: auto; margin-right: auto;">
 <thead>
  <tr>
   <th style="text-align:right;"> student </th>
   <th style="text-align:right;"> fruit </th>
   <th style="text-align:right;"> vegetable </th>
   <th style="text-align:right;"> icecream </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:right;"> 1 </td>
   <td style="text-align:right;"> 3 </td>
   <td style="text-align:right;"> 5 </td>
   <td style="text-align:right;"> 7 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 2 </td>
   <td style="text-align:right;"> 4 </td>
   <td style="text-align:right;"> 8 </td>
   <td style="text-align:right;"> 5 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 3 </td>
   <td style="text-align:right;"> 1 </td>
   <td style="text-align:right;"> 4 </td>
   <td style="text-align:right;"> 4 </td>
  </tr>
</tbody>
</table>
]