These are the default scales for the units class. These will
usually be added automatically. To override manually, use
scale_*_unit
.
1 2 3 4 5 6 7 8 9  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())

name 
The name of the scale. Used as axis or legend title. If

breaks 
One of:

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:

labels 
One of:

limits 
A numeric vector of length two providing limits of the scale.
Use 
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

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. Builtin 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 
position 
The position of the axis. "left" or "right" for vertical scales, "top" or "bottom" for horizontal scales 
sec.axis 
specifify a secondary axis 
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18  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))

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