Continuous ggplot2 Gradients from a biopalette Palette

Build a continuous colour or fill gradient from a sequential or diverging biopalette palette. The complete palette supplies the gradient stops to ggplot2::scale_colour_gradientn() or ggplot2::scale_fill_gradientn(). Gradients are interpolated in Lab colour space, the same space used when get_palette() resamples sequential and diverging palettes.

Usage

scale_color_biopalette_gradient(
  palette,
  ...,
  type = NULL,
  reverse = FALSE,
  values = NULL,
  midpoint = NULL,
  transform = "identity",
  palettes_dir = NULL
)

scale_colour_biopalette_gradient(
  palette,
  ...,
  type = NULL,
  reverse = FALSE,
  values = NULL,
  midpoint = NULL,
  transform = "identity",
  palettes_dir = NULL
)

scale_fill_biopalette_gradient(
  palette,
  ...,
  type = NULL,
  reverse = FALSE,
  values = NULL,
  midpoint = NULL,
  transform = "identity",
  palettes_dir = NULL
)

Arguments

palette

Character. Name of the palette.

...

Passed to ggplot2::scale_colour_gradientn() or ggplot2::scale_fill_gradientn(), for example name, breaks, labels, limits, transform, na.value, and guide.

type

Character. "sequential" or "diverging". If NULL, the type is detected automatically.

reverse

Logical. Reverse the palette. When values is supplied, its spacing is reversed with the colours. Default: FALSE.

values

Optional numeric positions for the palette colours, as accepted by ggplot2::scale_colour_gradientn(). Must have one value per palette colour, be non-decreasing, and lie in [0, 1].

midpoint

Optional finite numeric value to place at the visual centre of a diverging palette. Values are rescaled with equal units on either side of this point, so the shorter side of an asymmetric data range does not reach the palette's extreme colour. midpoint cannot be combined with values or a custom rescaler. The default, NULL, applies ordinary range-based scaling.

transform

A transformation specification accepted by ggplot2::continuous_scale(). The same transformation is applied to midpoint before the gradient is rescaled, so the centre remains correct under transformations such as "log10". Default: "identity".

palettes_dir

Character. Directory holding a palette collection. If NULL, the palettes bundled with the package are used.

Value

A ggplot2 continuous scale.

Details

Qualitative palettes are rejected because interpolating unordered category colours does not produce a meaningful continuous scale. Use scale_color_biopalette() or scale_fill_biopalette() for those palettes.

Examples

library(ggplot2)

ggplot(mtcars, aes(wt, mpg, colour = hp)) +
  geom_point(size = 3) +
  scale_color_biopalette_gradient("mitonuclear_blue")


ggplot(mtcars, aes(factor(cyl), factor(gear), fill = mpg - mean(mpg))) +
  geom_tile() +
  scale_fill_biopalette_gradient("walter_white", midpoint = 0)