## Usage

scale_alpha(..., range = c(0.1, 1))
scale_alpha_continuous(..., range = c(0.1, 1))
scale_alpha_discrete(..., range = c(0.1, 1))

## Arguments

- ...
- Other arguments passed on to
`continuous_scale`

or
`discrete_scale`

as appropriate, to control
name, limits, breaks, labels and so forth.
- range
- range of output alpha values. Should lie
between 0 and 1.

## Description

`scale_alpha`

is an alias for
`scale_alpha_continuous`

since that is the most
common use of alpha, and it saves a bit of typing.

## Examples

(p <- qplot(mpg, cyl, data = mtcars, alpha = cyl))

p + scale_alpha("cylinders")

p + scale_alpha("number\nof\ncylinders")

p + scale_alpha(range = c(0.4, 0.8))

(p <- qplot(mpg, cyl, data=mtcars, alpha = factor(cyl)))

p + scale_alpha_discrete(range = c(0.4, 0.8))