discretised_scale: Create discretised versions of continuous scales

In metR: Tools for Easier Analysis of Meteorological Fields

Create discretised versions of continuous scales

Description

This scale allows ggplot to understand data that has been discretised with some procedure akin to cut and access the underlying continuous values. For a scale that does the opposite (take continuous data and treat them as discrete) see ggplot2::binned_scale().

Usage

as.discretised_scale(scale_function)

scale_fill_discretised(
  ...,
  low = "#132B43",
  high = "#56B1F7",
  space = "Lab",
  na.value = "grey50",
  guide = ggplot2::guide_colorsteps(even.steps = FALSE, show.limits = TRUE),
  aesthetics = "fill"
)

scale_fill_divergent_discretised(
  ...,
  low = scales::muted("blue"),
  mid = "white",
  high = scales::muted("red"),
  midpoint = 0,
  space = "Lab",
  na.value = "grey50",
  guide = ggplot2::guide_colorsteps(even.steps = FALSE, show.limits = TRUE)
)

discretised_scale(
  aesthetics,
  scale_name,
  palette,
  name = ggplot2::waiver(),
  breaks = ggplot2::waiver(),
  labels = ggplot2::waiver(),
  limits = NULL,
  trans = scales::identity_trans(),
  na.value = NA,
  drop = FALSE,
  guide = ggplot2::guide_colorsteps(even.steps = FALSE),
  position = "left",
  rescaler = scales::rescale,
  oob = scales::censor,
  super = ScaleDiscretised
)

Arguments

scale_function	a scale function (e.g. scale_fill_divergent)
...	Arguments passed on to continuous_scale scale_name The name of the scale that should be used for error messages associated with this scale. palette A palette function that when called with a numeric vector with values between 0 and 1 returns the corresponding output values (e.g., scales::area_pal()). name The name of the scale. Used as the axis or legend title. If waiver(), the default, the name of the scale is taken from the first mapping used for that aesthetic. If NULL, the legend title will be omitted. breaks One of: NULL for no breaks waiver() for the default breaks computed by the transformation object A numeric vector of positions A function that takes the limits as input and returns breaks as output (e.g., a function returned by scales::extended_breaks()). Also accepts rlang lambda function notation. minor_breaks One of: NULL for no minor breaks waiver() for the default breaks (one minor break between each major break) A numeric vector of positions A function that given the limits returns a vector of minor breaks. Also accepts rlang lambda function notation. n.breaks An integer guiding the number of major breaks. The algorithm may choose a slightly different number to ensure nice break labels. Will only have an effect if breaks = waiver(). Use NULL to use the default number of breaks given by the transformation. labels One of: NULL for no labels waiver() for the default labels computed by the transformation object A character vector giving labels (must be same length as breaks) An expression vector (must be the same length as breaks). See ?plotmath for details. A function that takes the breaks as input and returns labels as output. Also accepts rlang lambda function notation. limits One of: NULL to use the default scale range A numeric vector of length two providing limits of the scale. Use NA to refer to the existing minimum or maximum A function that accepts the existing (automatic) limits and returns new limits. Also accepts rlang lambda function notation. Note that setting limits on positional scales will remove data outside of the limits. If the purpose is to zoom, use the limit argument in the coordinate system (see coord_cartesian()). rescaler A function used to scale the input values to the range [0, 1]. This is always scales::rescale(), except for diverging and n colour gradients (i.e., scale_colour_gradient2(), scale_colour_gradientn()). The rescaler is ignored by position scales, which always use scales::rescale(). Also accepts rlang lambda function notation. oob One of: Function that handles limits outside of the scale limits (out of bounds). Also accepts rlang lambda function notation. The default (scales::censor()) replaces out of bounds values with NA. scales::squish() for squishing out of bounds values into range. scales::squish_infinite() for squishing infinite values into range. trans For continuous scales, the name of a transformation object or the object itself. Built-in transformations include "asn", "atanh", "boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2", "logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal", "reverse", "sqrt" and "time". A transformation object bundles together a transform, its inverse, and methods for generating breaks and labels. Transformation objects are defined in the scales package, and are called ⁠<name>_trans⁠ (e.g., scales::boxcox_trans()). You can create your own transformation with scales::trans_new(). expand For position scales, a vector of range expansion constants used to add some padding around the data to ensure that they are placed some distance away from the axes. Use the convenience function expansion() to generate the values for the expand argument. The defaults are to expand the scale by 5% on each side for continuous variables, and by 0.6 units on each side for discrete variables. position For position scales, The position of the axis. left or right for y axes, top or bottom for x axes. super The super class to use for the constructed scale
low, high	Colours for low and high ends of the gradient.
space	colour space in which to calculate gradient. Must be "Lab" - other values are deprecated.
na.value	Colour to use for missing values
guide	Type of legend. Use "colourbar" for continuous colour bar, or "legend" for discrete colour legend.
aesthetics	Character string or vector of character strings listing the name(s) of the aesthetic(s) that this scale works with. This can be useful, for example, to apply colour settings to the colour and fill aesthetics at the same time, via aesthetics = c("colour", "fill").
mid	colour for mid point
midpoint	The midpoint (in data value) of the diverging scale. Defaults to 0.
scale_name	The name of the scale that should be used for error messages associated with this scale.
palette	A palette function that when called with a numeric vector with values between 0 and 1 returns the corresponding output values (e.g., scales::area_pal()).
name	The name of the scale. Used as the axis or legend title. If waiver(), the default, the name of the scale is taken from the first mapping used for that aesthetic. If NULL, the legend title will be omitted.
breaks	One of: NULL for no breaks waiver() for the default breaks computed by the transformation object A numeric vector of positions A function that takes the limits as input and returns breaks as output (e.g., a function returned by scales::extended_breaks()). Also accepts rlang lambda function notation.
labels	One of: NULL for no labels waiver() for the default labels computed by the transformation object A character vector giving labels (must be same length as breaks) An expression vector (must be the same length as breaks). See ?plotmath for details. A function that takes the breaks as input and returns labels as output. Also accepts rlang lambda function notation.
limits	One of: NULL to use the default scale range A numeric vector of length two providing limits of the scale. Use NA to refer to the existing minimum or maximum A function that accepts the existing (automatic) limits and returns new limits. Also accepts rlang lambda function notation. Note that setting limits on positional scales will remove data outside of the limits. If the purpose is to zoom, use the limit argument in the coordinate system (see coord_cartesian()).
trans	For continuous scales, the name of a transformation object or the object itself. Built-in transformations include "asn", "atanh", "boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2", "logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal", "reverse", "sqrt" and "time". A transformation object bundles together a transform, its inverse, and methods for generating breaks and labels. Transformation objects are defined in the scales package, and are called ⁠<name>_trans⁠ (e.g., scales::boxcox_trans()). You can create your own transformation with scales::trans_new().
drop	Should unused factor levels be omitted from the scale? The default, TRUE, uses the levels that appear in the data; FALSE uses all the levels in the factor.
position	For position scales, The position of the axis. left or right for y axes, top or bottom for x axes.
rescaler	A function used to scale the input values to the range [0, 1]. This is always scales::rescale(), except for diverging and n colour gradients (i.e., scale_colour_gradient2(), scale_colour_gradientn()). The rescaler is ignored by position scales, which always use scales::rescale(). Also accepts rlang lambda function notation.
oob	One of: Function that handles limits outside of the scale limits (out of bounds). Also accepts rlang lambda function notation. The default (scales::censor()) replaces out of bounds values with NA. scales::squish() for squishing out of bounds values into range. scales::squish_infinite() for squishing infinite values into range.
super	The super class to use for the constructed scale

Details

This scale makes it very easy to synchronise the breaks of filled contours and the breaks shown no the colour guide. Bear in mind that when using geom_contour_fill(), the default fill aesthetic (level_mid) is not discretised. To use this scale with that geom, you need to set aes(fill = after_stat(level)).

Value

A function with the same arguments as scale_function that works with discretised values.

See Also

scale_fill_discretised

Examples

library(ggplot2)
scale_fill_brewer_discretised <- as.discretised_scale(scale_fill_distiller)



library(ggplot2)

# Using the `level` compute aesthetic from `geom_contour_fill()`
# (or ggplot2::geom_contour_filled()), the default scale is discrete.
# This means that you cannot map colours to the underlying numbers.
v <- ggplot(faithfuld, aes(waiting, eruptions, z = density))
v + geom_contour_fill(aes(fill = after_stat(level)))

v + geom_contour_fill(aes(fill = after_stat(level))) +
  scale_fill_discretised()

# The scale can be customised the same as any continuous colour scale
v + geom_contour_fill(aes(fill = after_stat(level))) +
  scale_fill_discretised(low = "#a62100", high = "#fff394")

# Setting limits explicitly will truncate the scale
# (if any limit is inside the range of the breaks but doesn't
# coincide with any range, it will be rounded with a warning)
v + geom_contour_fill(aes(fill = after_stat(level))) +
  scale_fill_discretised(low = "#a62100", high = "#fff394",
                         limits = c(0.01, 0.028))

# Or extend it.
v + geom_contour_fill(aes(fill = after_stat(level))) +
  scale_fill_discretised(low = "#a62100", high = "#fff394",
                         limits = c(0, 0.07))

v + geom_contour_fill(aes(fill = after_stat(level))) +
  scale_fill_divergent_discretised(midpoint = 0.02)

# Existing continous scales can be "retrofitted" by changing the `super`
# and `guide` arguments.
v + geom_contour_fill(aes(fill = after_stat(level))) +
    scale_fill_distiller(super = ScaleDiscretised)

# Unequal breaks will, by default, map to unequal spacing in the guide
v + geom_contour_fill(aes(fill = after_stat(level)), breaks = c(0, 0.005, 0.01, 0.02, 0.04)) +
  scale_fill_discretised()

# You can change that by the `even.steps` argument on ggplot2::guide_colorsteps()
v + geom_contour_fill(aes(fill = after_stat(level)), breaks = c(0, 0.005, 0.01, 0.02, 0.04)) +
  scale_fill_discretised(guide = guide_colorsteps(even.steps = TRUE, show.limits = TRUE))

metR documentation built on Nov. 2, 2023, 6:01 p.m.