Position scales for units data

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Description

These are the default scales for the units class. These will usually be added automatically. To override manually, use scale_*_unit.

Usage

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scale_x_unit(name = waiver(), breaks = waiver(), unit = NULL,
  minor_breaks = waiver(), labels = waiver(), limits = NULL,
  expand = waiver(), oob = censor, na.value = NA_real_,
  trans = "identity", position = "bottom", sec.axis = waiver())

scale_y_unit(name = waiver(), breaks = waiver(), unit = NULL,
  minor_breaks = waiver(), labels = waiver(), limits = NULL,
  expand = waiver(), oob = censor, na.value = NA_real_,
  trans = "identity", position = "left", sec.axis = waiver())

Arguments

name

The name of the scale. Used as axis or legend title. If NULL, the default, the name of the scale is taken from the first mapping used for that aesthetic.

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

unit

A unit specification to use for the axis. If given, the values will be converted to this unit before plotting. An error will be thrown if the specified unit is incompatible with the unit of the data.

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.

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

limits

A numeric vector of length two providing limits of the scale. Use NA to refer to the existing minimum or maximum.

expand

A numeric vector of length two giving multiplicative and additive expansion constants. These constants ensure that the data is placed some distance away from the axes. The defaults are c(0.05, 0) for continuous variables, and c(0, 0.6) for discrete variables.

oob

Function that handles limits outside of the scale limits (out of bounds). The default replaces out of bounds values with NA.

na.value

Missing values will be replaced with this value.

trans

Either the name of a transformation object, or the object itself. Built-in transformations include "asn", "atanh", "boxcox", "exp", "identity", "log", "log10", "log1p", "log2", "logit", "probability", "probit", "reciprocal", "reverse" and "sqrt".

A transformation object bundles together a transform, it's inverse, and methods for generating breaks and labels. Transformation objects are defined in the scales package, and are called name_trans, e.g. boxcox_trans. You can create your own transformation with trans_new.

position

The position of the axis. "left" or "right" for vertical scales, "top" or "bottom" for horizontal scales

sec.axis

specifify a secondary axis

Examples

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library(units)
gallon <- make_unit('gallon')
mtcars$consumption <- mtcars$mpg * with(ud_units, mi/gallon)
mtcars$power <- mtcars$hp * with(ud_units, hp)

# Use units encoded into the data
ggplot(mtcars) +
    geom_point(aes(power, consumption))

# Convert units on the fly during plotting
ggplot(mtcars) +
    geom_point(aes(power, consumption)) +
    scale_x_unit(unit = 'W') +
    scale_y_unit(unit = 'km/l')

# Resolve units when transforming data
ggplot(mtcars) +
    geom_point(aes(power, 1/consumption))