Points linked by a segment

Source: R/geom-point-linked.r

The geometry "geom_point_s" provides a super set of the capabilities of geom geom_point from package 'ggplot2' by allowing plotting of arrows or segments joining the original position of displaced observations to their current position rendered as points or graphic symbols. The most common use is to demonstrate the action of different position functions. It can be also used to highlight observations.

geom_point_s(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  nudge_x = 0,
  nudge_y = 0,
  move.point = TRUE,
  arrow = grid::arrow(length = unit(1/3, "lines"), ends = "first"),
  default.colour = "black",
  default.color = default.colour,
  colour.target = "point",
  color.target = colour.target,
  default.alpha = NA,
  alpha.target = "all",
  add.segments = TRUE,
  box.padding = 0.25,
  point.padding = 1e-06,
  segment.linewidth = 0.5,
  min.segment.length = 0,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Arguments

mapping

Set of aesthetic mappings created by aes. If specified and inherit.aes = TRUE (the default), is combined with the default mapping at the top level of the plot. You only need to supply mapping if there isn't a mapping defined for the plot.

data

A data frame. If specified, overrides the default data frame defined at the top level of the plot.

stat

The statistical transformation to use on the data for this layer, as a string.

position

Position adjustment, either as a string, or the result of a call to a position adjustment function.

...

other arguments passed on to layer. There are three types of arguments you can use here:

  • Aesthetics: to set an aesthetic to a fixed value, like colour = "red" or size = 3.

  • Other arguments to the layer, for example you override the default stat associated with the layer.

  • Other arguments passed on to the stat.

nudge_x, nudge_y

Horizontal and vertical adjustments to nudge the starting position of each text label. The units for nudge_x and nudge_y are the same as for the data units on the x-axis and y-axis.

move.point

logical If TRUE the point is drawn at the nudged position while if FALSE the point is drawn at the original position.

arrow

specification for arrow heads, as created by arrow

default.colour, default.color

A colour definition to use for elements not targeted by the colour aesthetic.

colour.target, color.target

A character string, one of "all", "point" and "segment" or "none".

default.alpha

numeric in [0..1] A transparency value to use for elements not targeted by the alpha aesthetic.

alpha.target

A character string, one of "all", "segment", "point", or "none".

add.segments

logical Display connecting segments or arrows between original positions and displaced ones if both are available.

box.padding, point.padding

numeric By how much each end of the segments should shortened in mm.

segment.linewidth

numeric Width of the segments or arrows in mm.

min.segment.length

numeric Segments shorter that the minimum length are not rendered, in mm.

na.rm

If FALSE (the default), removes missing values with a warning. If TRUE silently removes missing values.

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes.

inherit.aes

If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders.

Value

A plot layer instance.

Details

The plotting of segments is similar in idea to that implemented in geom_text_repel and relies on position functions that rename instead of only replacing the original x and y coordinates from the data object.

By default this geom uses position_nudge_center which is backwards compatible with position_nudge but provides additional control on the direction of the nudging.

Note

The insets are stored nested within the main ggplot object and contain their own copy of the data, and are rendered as grid grobs as normal ggplots at the time the main ggplot is rendered. They can have different themes.

Use annotate as redefined in 'ggpp' when adding insets as annotations (automatically available unless 'ggpp' is not attached). annotate cannot be used with the npcx and npcy pseudo-aesthetics.

Position functions

Many layer functions from package 'ggpp' are designed to work seamlessly with position functions that keep, rather than discard, the original x and y positions in data when computing a new displaced position. See position_nudge_keep, position_dodge_keep, position_jitter_keep, position_nudge_center, position_nudge_line, position_nudge_to, position_dodgenudge, position_jitternudge, and position_stacknudge for examples and details of their use.

See also

geom_point.

Examples


# Same output as with geom_point()
ggplot(mpg[1:20, ],
       aes(cyl, hwy)) +
  geom_point_s(colour = "blue")


# with segment drawn after nudging
ggplot(mpg[1:20, ],
       aes(cyl, hwy, label = drv)) +
  geom_point_s(position = position_nudge_keep(x = 0.2),
               colour = "red") +
  geom_point_s(colour = "blue") +
  expand_limits(x = c(3.5, 8.5))


ggplot(mpg[1:20, ],
       aes(cyl, hwy, label = drv)) +
  geom_point_s(position = position_nudge_keep(x = 0.2),
               colour = "blue",
               move.point = FALSE) +
  expand_limits(x = c(3.5, 8.5))


# with segment drawn after nudging
ggplot(mpg[1:20, ],
       aes(cyl, hwy, label = drv)) +
  geom_point_s(position = position_nudge_keep(x = 0.2),
               colour = "red",
               colour.target = "all") +
  geom_point_s(colour = "blue")


ggplot(mpg[1:20, ],
       aes(cyl, hwy, label = drv)) +
  geom_point_s(position = position_nudge_keep(x = 0.2),
               colour = "red",
               colour.target = "segment") +
  geom_point_s(colour = "blue")


ggplot(mpg[1:20, ],
       aes(cyl, hwy, label = drv)) +
  geom_point_s(position = position_nudge_keep(x = 0.2),
               colour = "red",
               colour.target = "point") +
  geom_point_s(colour = "blue")


ggplot(mpg[1:50, ],
       aes(cyl, hwy, label = drv)) +
  geom_point_s(position = position_jitternudge(width = 0.66, height = 2,
                                               seed = 456,
                                               nudge.from = "jittered",
                                               kept.origin = "original"),
               colour = "red",
               alpha = 0.3, alpha.target = "segment",
               arrow = grid::arrow(length = grid::unit(0.4, "lines"),
                                   ends = "first")) +
  geom_point_s(colour = "blue")