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Partition a layer into subgroups (Layer operation)

Source: R/operation-partition.R
partition.Rd

A layer operation for adding a partition aesthetic to a layer.

Usage

partition(object, partition)

Arguments

object

One of:

  • A layer-like object: applies this operation to the layer.

  • A missing argument: creates an operation

  • Anything else: creates an operation, passing object along to the partition argument

partition

One of:

  • A list of quosures, such as returned by dplyr::vars(), giving a (possibly multi-) column expression for the partition aesthetic. These expressions are combined using interaction() to be passed on to aes(partition = ...)

  • A one-sided formula, giving a single-column expression for the partition aesthetic, which is passed on to aes_(partition = ...).

Value

A layer-like object (if object is layer-like) or an operation (if not).

Details

This is a shortcut for setting the partition aesthetic of a layer.

  • partition(~ XXX) is roughly equivalent to adjust(aes(partition = XXX))

  • partition(vars(X, Y, ...)) is roughly equivalent to adjust(aes(partition = interaction(X, Y, ...)))

When a layer with a partition aesthetic is used by the following operations, the effects of the operations are applied across groups:

  • blend(): Blends graphical objects within the subgroups defined by the partition together using normal ("over") blending before applying its blend between subgroups.

See also

operation for a description of layer operations.

Other layer operations: adjust, affine_transform, blend, copy, nop

Examples

library(ggplot2)

# create two versions of a dataset, where draw order can affect output
set.seed(1234)
df_a = data.frame(x = rnorm(500, 0), y = rnorm(500, 1), set = "a")
df_b = data.frame(x = rnorm(500, 1), y = rnorm(500, 2), set = "b")
df_ab = rbind(df_a, df_b) |>
  transform(order = "draw a then b")
df_ba = rbind(df_b, df_a) |>
  transform(order = "draw b then a")
df = rbind(df_ab, df_ba)

# Using the "multiply" blend mode, draw order does not matter, but
# the "multiply" blend is applied to all points, creating dark regions
# outside the intersection:
df |>
  ggplot(aes(x, y, color = set)) +
  geom_point(size = 3, alpha = 0.5) |> blend("multiply") +
  scale_color_brewer(palette = "Set1") +
  facet_grid(~ order)


# By partitioning (either through |> partition(vars(set)) or aes(partition = set))
# we will blend using the default blend mode (over) first, then we can apply the
# "multiply" blend just between the two sets, so the regions outside the
# intersection are not blended using "multiply":
df |>
  ggplot(aes(x, y, color = set, partition = set)) +
  geom_point(size = 3, alpha = 0.5) |> blend("multiply") +
  scale_color_brewer(palette = "Set1") +
  facet_grid(~ order)