`R/as-discretised-scale.R`

, `R/scale-unbinned.R`

`discretised_scale.Rd`

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()`

.

```
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
)
```

- 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 objectA 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 (none for discrete, one minor break between each major break for continuous)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 break positions.

`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 objectA 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 rangeA numeric vector of length two providing limits of the scale. Use

`NA`

to refer to the existing minimum or maximumA 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`

`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 objectA 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 objectA 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 rangeA numeric vector of length two providing limits of the scale. Use

`NA`

to refer to the existing minimum or maximumA 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
- 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

A function with the same arguments as `scale_function`

that works with discretised
values.

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))`

.

scale_fill_discretised

```
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))
#> Warning: User supplied limits don't correspond to valid breaks. [0.01, 0.028] rounded to [0.01, 0.03]
# 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))
```