Data Visualization

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# Data Visualization
## Colour
### Andrew Irwin, <a href="mailto:a.irwin@dal.ca" class="email">a.irwin@dal.ca</a>
### Math & Stats, Dalhousie University
### 2021-03-24 (updated: 2021-03-12)

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# Plan

* Discrete colour scales

* Continuous colour scales

* viridis colour

* other palettes

* custom colours

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### Colour guidelines - Discrete

* Not too many

* Keep brightness constant

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### Colour guidelines - Continuous

* One shade, vary brightness

* Two shades if there is a natural middle or 0, white in middle

* Avoid red-green diverging scales

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### Discrete colour scales

```r
penguins %>% ggplot(aes(body_mass_g, flipper_length_mm,
                        color = species)) + geom_point() + my_theme
```

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### Discrete colour scales

```r
penguins %>% ggplot(aes(body_mass_g, flipper_length_mm,
                        color = species)) + geom_point() + my_theme +
  scale_color_viridis_d(end = 0.7) 
```

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### Discrete colour scales

```r
penguins %>% ggplot(aes(body_mass_g, flipper_length_mm,
                        color = species)) + geom_point() + my_theme +
  scale_color_paletteer_d("ggthemes::hc_default")
```

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### Discrete colour scales

```r
penguins %>% ggplot(aes(body_mass_g, flipper_length_mm,
                        color = species)) + geom_point() + my_theme +
  scale_color_manual(values = c("red", "blue", "orange"))
```

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### Continuous colour shades

```r
gapminder %>% filter(country %in% c("Canada", "China", "Chile", "Iceland")) %>%
  ggplot(aes(year, lifeExp, color = log10(pop))) +
  geom_point(size=3) + my_theme
```

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### Continuous colour shades - diverging

```r
p1 <- penguins %>% mutate(body_mass_centered = 
                      body_mass_g - mean(body_mass_g, na.rm=TRUE)) %>%
  ggplot(aes(flipper_length_mm, bill_length_mm, 
             color = body_mass_centered)) +
  geom_point(size=3) + theme_bw() +
  # scale_color_distiller(type="div", palette="RdBu", limits = c(-2000,2000)) 
  scale_color_fermenter(type="div", 
                        palette="RdBu", 
                        limits = c(-2000,2000)) 
```

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### Continuous colour shades - diverging

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# Further reading

* Course notes

* Healy and Wilke sections on colour

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## Task

* Practice using colour

* No assigned task