Binned colour gradients: scale_steps

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_steps(), which covers scale_colour_steps2(), scale_colour_stepsn(), scale_fill_steps(), scale_fill_steps2() and scale_fill_stepsn() 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.

The steps scales are the binned counterparts of the gradient scales: they cut a continuous column into bins and give each bin one colour from a gradient. scale_colour_steps() runs from a low colour to a high one, scale_colour_steps2() diverges from a low colour through a middle one to a high one, around a midpoint, and scale_colour_stepsn() takes its colours from as many as it is given; the fill versions do the same for fill. Giggly has none of this yet: it has no binned scales, and colours a continuous column along a gradient, unbinned, as Giggly.Plot.scale_color_gradient/2 and its kin do.

A binned gradient

The examples draw from a table of random numbers R makes after set.seed(1).

set.seed(1)
df <- data.frame(
  x = runif(100),
  y = runif(100),
  z1 = rnorm(100)
)

# Use scale_colour_steps for a standard binned gradient
ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z1)) +
  scale_colour_steps()

Not in Giggly yet: scale_colour_steps().

A diverging binned gradient

# Get a divergent binned scale with the *2 variant
ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z1)) +
  scale_colour_steps2()

Not in Giggly yet: scale_colour_steps2().

Colours of your own

# Define your own colour ramp to extract binned colours from
ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z1)) +
  scale_colour_stepsn(colours = terrain.colors(10))

Not in Giggly yet: scale_colour_stepsn().