Define aesthetic mappings programmatically
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.
All these functions are soft-deprecated. Please use tidy evaluation
idioms instead (see the quasiquotation section in
aes()
documentation).
# 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))
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