Layer operations

Layer operations are composable transformations that can be applied to ggplot2 layer-like objects, such as stats, geoms, and lists of stats and geoms; see the layer-like documentation page for a description of valid layer-like objects.

Usage

# S4 method for class 'operation'
show(object)

# S4 method for class 'operation'
format(x, ...)

# S4 method for class 'adjust'
format(x, ...)

# S4 method for class 'affine_transform'
format(x, ...)

# S4 method for class 'blend'
format(x, ...)

# S4 method for class 'operation_composition'
format(x, ...)

# S4 method for class 'nop'
format(x, ...)

# S4 method for class 'operation_product'
format(x, ...)

Arguments

x, object

An operation.

...

Further arguments passed to other methods.

Value

For show(), an invisible() copy of the input.

For format(), a character string representing the input.

Details

operations can be composed using the + and * operators (see operation_sum and operation_product). Addition and multiplication of operations and layer-like objects obeys the distributive law.

operations can be applied to layer-like objects using * or |>, with slightly different results:

• Using *, application of operations to a list of layer-like objects is distributive. For example, list(geom_line(), geom_point()) * blend("multiply") is equivalent to list(geom_line() * blend("multiply"), geom_point() * blend("multiply")); i.e. it multiply-blends the contents of the two layers individually.

• Using |>, application of operations to a list of layer-like objects is not distributive (unless the only reasonable interpretation of applying the transformation is necessarily distributive; e.g. adjust()). For example, list(geom_line(), geom_point()) |> blend("multiply") would multiply-blend both layers together, rather than multiply-blending the contents of the two layers individually.

Methods (by generic)

• show(operation): Print an operation.

• format(operation): Format an operation for printing.

Examples

library(ggplot2)

# operations can stand alone
adjust(aes(color = x))
#> <operation>: adjust(aes(colour = ~x))

# they can also be applied to layers through multiplication or piping
geom_line() |> adjust(aes(color = x))
#> mapping: colour = ~x 
#> geom_line: na.rm = FALSE, orientation = NA, arrow = NULL, arrow.fill = NULL, lineend = butt, linejoin = round, linemitre = 10
#> stat_identity: na.rm = FALSE
#> position_identity 
geom_line() * adjust(aes(color = x))
#> mapping: colour = ~x 
#> geom_line: na.rm = FALSE, orientation = NA, arrow = NULL, arrow.fill = NULL, lineend = butt, linejoin = round, linemitre = 10
#> stat_identity: na.rm = FALSE
#> position_identity 

# layer operations act as a small algebra, and can be combined through
# multiplication and addition
(adjust(fill = "green") + 1) * blend("multiply")
#> <operation>: (adjust(fill = "green") * blend("multiply") + blend("multiply"))