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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_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.


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.

Life cycle

All these functions are soft-deprecated. Please use tidy evaluation idioms instead. Regarding aes_string(), you can replace it with .data pronoun. For example, the following code can achieve the same mapping as aes_string(x_var, y_var).

x_var <- "foo"
y_var <- "bar"
aes(.data[[x_var]], .data[[y_var]])

For more details, please see vignette("ggplot2-in-packages").

See also