| aes_ {ggplot2} | R Documentation |
Aesthetic mappings describe how variables in the data are mapped to visual
properties (aesthetics) of geoms. aes uses non-standard
evaluation to capture the variable names. aes_ and aes_string
require you to explicitly quote the inputs either with "" for
aes_string(), or with quote or ~ for aes_().
(aes_q is an alias to aes_). This makes aes_ and
aes_string easy to program with.
aes_(x, y, ...) aes_string(x, y, ...) aes_q(x, y, ...)
x, y, ... |
List of name value pairs. Elements must be either quoted calls, strings, one-sided formulas or constants. |
aes_string and aes_ are particularly useful when writing
functions that create plots because you can use strings or quoted
names/calls to define the aesthetic mappings, rather than having to use
substitute to generate a call to aes().
I recommend using aes_(), because creating the equivalents of
aes(colour = "my colour") or aes{x = `X$1`}
with aes_string() is quite clunky.
# Three ways of generating the same aesthetics
aes(mpg, wt, col = cyl)
aes_(quote(mpg), quote(wt), col = quote(cyl))
aes_(~mpg, ~wt, col = ~cyl)
aes_string("mpg", "wt", col = "cyl")
# You can't easily mimic these calls with aes_string
aes(`$100`, colour = "smooth")
aes_(~ `$100`, colour = "smooth")
# Ok, you can, but it requires a _lot_ of quotes
aes_string("`$100`", colour = '"smooth"')
# Convert strings to names with as.name
var <- "cyl"
aes(col = x)
aes_(col = as.name(var))