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Discrete colour scales: scale_colour_discrete

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Discrete colour scales: scale_colour_discrete

Mix.install([
  {:giggly, path: Path.join(__DIR__, "..")},
  {:kino, "~> 0.19"}
  ])

About this notebook

This notebook follows the examples on ggplot2's reference page for scale_colour_discrete(), which covers scale_fill_discrete() too, in the order the page gives them. Each example shows ggplot2's code first and then Giggly's. An example Giggly cannot draw yet keeps its ggplot2 code and names what it is waiting for, so the page is also a list of what remains.

scale_colour_discrete() and scale_fill_discrete() are the scales ggplot2 uses by default when a column of discrete values is mapped to colour or fill, giving each value its own colour from a palette. Their default palette is a setting of the theme. Giggly draws a discrete column mapped to colour or fill as scale_colour_discrete() does by default, in hues evenly spaced round the colour wheel with a legend, and has Giggly.Plot.scale_color_discrete/2 and Giggly.Plot.scale_fill_discrete/2, whose palette: is a list of colours, but no palette given as a function, such as scales::pal_brewer(), and takes no palette from the theme (palette.colour.discrete).

A palette given to the scale

scales::pal_brewer() is a palette from the scales package, here ColorBrewer's Dark2.

# A standard plot
p <- ggplot(mpg, aes(displ, hwy, colour = class)) +
  geom_point()

# You can use the scale to give a palette directly
p + scale_colour_discrete(palette = scales::pal_brewer(palette = "Dark2"))

Not in Giggly yet: scales::pal_brewer().

A palette from the theme

# The default colours are encoded into the theme
p + theme(palette.colour.discrete = scales::pal_grey())

Not in Giggly yet: the theme's palette.colour.discrete setting and scales::pal_grey().

A default for every plot

update_theme() changes the theme every later plot is drawn in, and returns the one it replaced. Giggly has no global settings: every option is an argument.

# You can globally set default colour palette via the theme
old <- update_theme(palette.colour.discrete = scales::pal_viridis())

# Plot now shows new global default
p

Not in Giggly yet: the theme's palette.colour.discrete setting and scales::pal_viridis().

Restoring the theme

# Restoring the previous theme
theme_set(old)

theme_set() makes the theme saved in old the default again, undoing update_theme(). It draws nothing. Giggly has no global settings, so there is nothing to restore.

Other notebooks:

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