R: Create your own discrete scale

scale_manual {ggplot2}

R Documentation

Create your own discrete scale

Description

These functions allow you to specify your own set of mappings from levels in the data to aesthetic values.

Usage

scale_colour_manual(..., values, aesthetics = "colour")

scale_fill_manual(..., values, aesthetics = "fill")

scale_size_manual(..., values)

scale_shape_manual(..., values)

scale_linetype_manual(..., values)

scale_alpha_manual(..., values)

scale_discrete_manual(aesthetics, ..., values)

Arguments

...

Arguments passed on to discrete_scale

breaks

One of:

NULL for no breaks
waiver() for the default breaks computed by the transformation object
A character vector of breaks
A function that takes the limits as input and returns breaks as output

limits

A character vector that defines possible values of the scale and their order.

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.

na.translate

Unlike continuous scales, discrete scales can easily show missing values, and do so by default. If you want to remove missing values from a discrete scale, specify na.translate = FALSE.

na.value

If na.translate = TRUE, what value aesthetic value should missing be displayed as? Does not apply to position scales where NA is always placed at the far right.

scale_name

The name of the scale

palette

A palette function that when called with a single integer argument (the number of levels in the scale) returns the values that they should take

name

The name of the scale. Used as 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.

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)
A function that takes the breaks as input and returns labels as output

guide

A function used to create a guide or its name. See guides() for more info.

super

The super class to use for the constructed scale

values

a set of aesthetic values to map data values to. If this is a named vector, then the values will be matched based on the names. If unnamed, values will be matched in order (usually alphabetical) with the limits of the scale. Any data values that don't match will be given na.value.

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").

Details

The functions scale_colour_manual(), scale_fill_manual(), scale_size_manual(), etc. work on the aesthetics specified in the scale name: colour, fill, size, etc. However, the functions scale_colour_manual() and scale_fill_manual() also have an optional aesthetics argument that can be used to define both colour and fill aesthetic mappings via a single function call (see examples). The function scale_discrete_manual() is a generic scale that can work with any aesthetic or set of aesthetics provided via the aesthetics argument.

Examples

p <- ggplot(mtcars, aes(mpg, wt)) +
  geom_point(aes(colour = factor(cyl)))
p + scale_colour_manual(values = c("red", "blue", "green"))

# It's recommended to use a named vector
cols <- c("8" = "red", "4" = "blue", "6" = "darkgreen", "10" = "orange")
p + scale_colour_manual(values = cols)

# You can set color and fill aesthetics at the same time
ggplot(
  mtcars,
  aes(mpg, wt, colour = factor(cyl), fill = factor(cyl))
) +
  geom_point(shape = 21, alpha = 0.5, size = 2) +
  scale_colour_manual(
    values = cols,
    aesthetics = c("colour", "fill")
  )

# As with other scales you can use breaks to control the appearance
# of the legend.
p + scale_colour_manual(values = cols)
p + scale_colour_manual(
  values = cols,
  breaks = c("4", "6", "8"),
  labels = c("four", "six", "eight")
)

# And limits to control the possible values of the scale
p + scale_colour_manual(values = cols, limits = c("4", "8"))
p + scale_colour_manual(values = cols, limits = c("4", "6", "8", "10"))

[Package ggplot2 version 3.0.0 Index]