Add Grobs on the margins

Margin grobs can supplement a 2d display with annotations. Margin grobs such as icons or symbols can highlight individual values along a margin. The geometries geom_x_margin_grob() and geom_y_margin_grob() behave similarly geom_vline() and geom_hline() and share their "double personality" as both annotations and geometries.

Usage

geom_x_margin_grob(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  xintercept,
  sides = "b",
  grob.shift = 0,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = FALSE
)

geom_y_margin_grob(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  yintercept,
  sides = "l",
  grob.shift = 0,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = FALSE
)

Arguments

mapping: The aesthetic mapping, usually constructed with aes. Only needs to be set at the layer level if you are overriding the plot defaults.
data: A layer specific dataset - only needed if you want to override the plot defaults.
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. This can include aesthetics whose values you want to set, not map. See layer for more details.
xintercept, yintercept: numeric Parameters that control the position of the marginal points. If these are set, data, mapping and show.legend are overridden.
sides: A character string of length one that controls on which side of the plot the grob annotations appear on. It can be set to a string containing one of "t", "r", "b" or "l", for top, right, bottom, and left.
grob.shift: numeric value expressed in npc units for the shift of the marginal grob inwards from the edge of the plotting area.
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.

Alignment

You can modify text alignment with the vjust and hjust aesthetics. These can either be a number between 0 (right/bottom) and 1 (top/left) or a character ("left", "middle", "right", "bottom", "center", "top"). In addition, you can use special alignments for justification including "position", "inward" and "outward". Inward always aligns text towards the center of the plotting area, and outward aligns it away from the center of the plotting area. If tagged with _mean or _median (e.g., "outward_mean") the mean or median of the data in the panel along the corresponding axis is used as center. If the characters following the underscore represent a number (e.g., "outward_10.5") the reference point will be this value in data units. Position justification is computed based on the direction of the displacement of the position of the label so that each individual text or label is justified outwards from its original position. The default justification is "position".

If no position displacement is applied, or a position function defined in 'ggplot2' is used, these geometries behave similarly to the corresponding ones from package 'ggplot2' with a default justification of 0.5 and no segment drawn.

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.

Examples

# We can add icons to the margin of a plot to signal events