Tips for effective data visualization

# Tips for effective data visualization
## <br><br> Introduction to Data Science
### <a href="https://introds.org/">introds.org</a>
### <br> Dr. Mine Çetinkaya-Rundel

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<span>
<a href="https://introds.org" target="_blank">introds.org</a>
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# Designing effective visualizations

---

## Keep it simple

.pull-left-narrow[
<img src="img/pie-3d.jpg" width="100%" style="display: block; margin: auto;" />
]
.pull-right-wide[
<img src="w5-d02-effective-dataviz_files/figure-html/pie-to-bar-1.png" width="100%" style="display: block; margin: auto;" />
]

---

## Use	color	to	draw	attention

.pull-left[
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-2-1.png" width="100%" style="display: block; margin: auto;" />
]
.pull-right[
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-3-1.png" width="100%" style="display: block; margin: auto;" />
]

---

## Tell a story

---

# Principles	for	effective	visualizations

---

## Principles	for	effective	visualizations

- Order matters
- Put long categories on the y-axis
- Keep	scales consistent
- Select meaningful colors
- Use meaningful and nonredundant labels

---

## Data

In September 2019, YouGov survey asked 1,639 GB adults the following question:

.pull-left[
> In hindsight, do you think Britain was right/wrong to vote to leave EU?
>
>- Right to leave  
>- Wrong to leave  
>- Don't know

]
.pull-right[

<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-6-1.png" width="100%" style="display: block; margin: auto;" />
]

.footnote[ 
Source: [YouGov Survey Results](https://d25d2506sfb94s.cloudfront.net/cumulus_uploads/document/x0msmggx08/YouGov%20-%20Brexit%20and%202019%20election.pdf), retrieved Oct 7, 2019
]

---

# Order matters

---

## Alphabetical order is rarely ideal

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-7-1.png" width="60%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(x = opinion)) +
  geom_bar()
```
]

]

---

## Order by frequency

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-8-1.png" width="60%" style="display: block; margin: auto;" />
]

`fct_infreq`: Reorder factors' levels by frequency

```r
*ggplot(brexit, aes(x = fct_infreq(opinion))) +
  geom_bar()
```
]

]

---

## Clean up labels

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-9-1.png" width="60%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(x = opinion)) +
  geom_bar() +
* labs(
*   x = "Opinion",
*   y = "Count"
* )
```
]

]

---

## Alphabetical order is rarely ideal

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-10-1.png" width="60%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(x = region)) +
  geom_bar()
```
]

]

---

## Use inherent level order

`fct_relevel`: Reorder factor levels using a custom order

```r
brexit <- brexit %>%
  mutate(
*   region = fct_relevel(
      region,
      "london", "rest_of_south", "midlands_wales", "north", "scot"
    )
  )
```
]

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-11-1.png" width="60%" style="display: block; margin: auto;" />
]

]

---

## Clean up labels

`fct_recode`: Change factor levels by hand

```r
brexit <- brexit %>%
  mutate(
*   region = fct_recode(
      region,
      London = "london",
      `Rest of South` = "rest_of_south",
      `Midlands / Wales` = "midlands_wales",
      North = "north",
      Scotland = "scot"
    )
  )
```
]

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/recode-plot-1.png" width="60%" style="display: block; margin: auto;" />
]

]

---

# Put long categories on the y-axis

---

## Long categories can be hard to read

---

## Move them to the y-axis

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-13-1.png" width="60%" style="display: block; margin: auto;" />
]

```r
*ggplot(brexit, aes(y = region)) +
  geom_bar()
```
]

]

---

## And reverse the order of levels

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-14-1.png" width="60%" style="display: block; margin: auto;" />
]

`fct_rev`: Reverse order of factor levels

```r
*ggplot(brexit, aes(y = fct_rev(region))) +
  geom_bar()
```
]

]

---

## Clean up labels

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-15-1.png" width="60%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = fct_rev(region))) +
  geom_bar() +
* labs(
*   x = "Count",
*   y = "Region"
* )
```
]

]

---

# Pick a purpose

---

## Segmented bar plots can be hard to read

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-16-1.png" width="60%" style="display: block; margin: auto;" />
]

```r
*ggplot(brexit, aes(y = region, fill = opinion)) +
  geom_bar()
```
]

]

---

## Use facets

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-17-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = region)) +
  geom_bar() +
* facet_wrap(~region, nrow = 1)
```
]

]

---

## Avoid redundancy?

---

## Redundancy can help tell a story

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-19-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1)
```
]

]

---

## Be selective with redundancy

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-20-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1) +
* guides(fill = FALSE)
```
]

]

---

## Use informative labels

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-21-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1) +
  guides(fill = FALSE) +
  labs(
*   title = "Was Britain right/wrong to vote to leave EU?",
    x = NULL, y = NULL
  )
```
]

]

---

## A bit more info

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-22-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1) +
  guides(fill = FALSE) +
  labs(
    title = "Was Britain right/wrong to vote to leave EU?",
*   subtitle = "YouGov Survey Results, 2-3 September 2019",
*   caption = "Source: https://d25d2506sfb94s.cloudfront.net/cumulus_uploads/document/x0msmggx08/YouGov%20-%20Brexit%20and%202019%20election.pdf",
    x = NULL, y = NULL
  )
```
]

]

---

## Let's do better

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-23-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1) +
  guides(fill = FALSE) +
  labs(
    title = "Was Britain right/wrong to vote to leave EU?",
    subtitle = "YouGov Survey Results, 2-3 September 2019",
*   caption = "Source: bit.ly/2lCJZVg",
    x = NULL, y = NULL
  )
```
]

]

---

## Fix up facet labels

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-24-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region,
    nrow = 1,
*   labeller = label_wrap_gen(width = 12)
  ) + 
  guides(fill = FALSE) +
  labs(
    title = "Was Britain right/wrong to vote to leave EU?",
    subtitle = "YouGov Survey Results, 2-3 September 2019",
    caption = "Source: bit.ly/2lCJZVg",
    x = NULL, y = NULL
  )
```
]

]

---

# Select meaningful colors

---

## Rainbow colors not always the right choice

---

## Manually choose colors when needed

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-26-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1, labeller = label_wrap_gen(width = 12)) +
  guides(fill = FALSE) +
  labs(title = "Was Britain right/wrong to vote to leave EU?",
       subtitle = "YouGov Survey Results, 2-3 September 2019",
       caption = "Source: bit.ly/2lCJZVg",
       x = NULL, y = NULL) +
* scale_fill_manual(values = c(
*   "Wrong" = "red",
*   "Right" = "green",
*   "Don't know" = "gray"
* ))
```
]

]

---

## Choosing better colors

---

## Use better colors

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-28-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1, labeller = label_wrap_gen(width = 12)) +
  guides(fill = FALSE) +
  labs(title = "Was Britain right/wrong to vote to leave EU?",
       subtitle = "YouGov Survey Results, 2-3 September 2019",
       caption = "Source: bit.ly/2lCJZVg",
       x = NULL, y = NULL) +
  scale_fill_manual(values = c(
*   "Wrong" = "#ef8a62",
*   "Right" = "#67a9cf",
*   "Don't know" = "gray"
  ))
```
]

]

---

## Select theme

.panel[.panel-name[Plot]
<img src="w5-d02-effective-dataviz_files/figure-html/unnamed-chunk-29-1.png" width="90%" style="display: block; margin: auto;" />
]

```r
ggplot(brexit, aes(y = opinion, fill = opinion)) +
  geom_bar() +
  facet_wrap(~region, nrow = 1, labeller = label_wrap_gen(width = 12)) +
  guides(fill = FALSE) +
  labs(title = "Was Britain right/wrong to vote to leave EU?",
       subtitle = "YouGov Survey Results, 2-3 September 2019",
       caption = "Source: bit.ly/2lCJZVg",
       x = NULL, y = NULL) +
  scale_fill_manual(values = c("Wrong" = "#ef8a62",
                               "Right" = "#67a9cf",
                               "Don't know" = "gray")) +
* theme_minimal()
```
]

]

---

.your-turn[
### .hand[Your turn!]
.midi[
- RStudio Cloud > `AE 07 - Brexit + Telling stories with dataviz` > `brexit.Rmd`. 
- Change the visualisation in three different ways to tell slightly different stories with it each time.
]
]