discretised_scale() R function from [metR]

Create discretised versions of continuous scales

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(). data


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::pal_area()).

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()`). Note that for position scales, limits are provided after scale expansion. 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. When the function has two arguments, it will be given the limits and major breaks.

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: Deprecated in favour of transform.
call: The call used to construct the scale for reporting messages.
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::pal_area()).
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()). Note that for position scales, limits are provided after scale expansion. 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: Deprecated in favour of transform.
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

Returns

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

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)).

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))

discretised_scale function

Create discretised versions of continuous scales

Arguments

Returns

Details

Examples

See Also