Add arrows to swimmer plot lanes — geom_swim

Arrows attached to the end of swimmer plot lanes can be used to denote the continuation of events such as ongoing treatment, implying that the activity or status extends beyond the plotted period.

Usage

geom_swim_arrow(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  arrow_colour = "black",
  arrow_head_length = unit(0.25, "inches"),
  arrow_neck_length = NULL,
  arrow_fill = NULL,
  arrow_type = "closed",
  lineend = "butt",
  linejoin = "round",
  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), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.

data

A data frame prepared for use with geom_swim_arrow(). Required.

stat

The statistical transformation to use on the data for this layer. When using a geom_*() function to construct a layer, the stat argument can be used to override the default coupling between geoms and stats. The stat argument accepts the following:

A Stat ggproto subclass, for example StatCount.
A string naming the stat. To give the stat as a string, strip the function name of the stat_ prefix. For example, to use stat_count(), give the stat as "count".
For more information and other ways to specify the stat, see the layer stat documentation.

position

Position adjustment. ggswim accepts either "stack" or "identity" depending on the use case. Default is "identity".

...

Other arguments passed on to layer()'s params argument. These arguments broadly fall into one of 4 categories below. Notably, further arguments to the position argument, or aesthetics that are required can not be passed through .... Unknown arguments that are not part of the 4 categories below are ignored.

Static aesthetics that are not mapped to a scale, but are at a fixed value and apply to the layer as a whole. For example, colour = "red" or linewidth = 3. The geom's documentation has an Aesthetics section that lists the available options. The 'required' aesthetics cannot be passed on to the params. Please note that while passing unmapped aesthetics as vectors is technically possible, the order and required length is not guaranteed to be parallel to the input data.
When constructing a layer using a stat_*() function, the ... argument can be used to pass on parameters to the geom part of the layer. An example of this is stat_density(geom = "area", outline.type = "both"). The geom's documentation lists which parameters it can accept.
Inversely, when constructing a layer using a geom_*() function, the ... argument can be used to pass on parameters to the stat part of the layer. An example of this is geom_area(stat = "density", adjust = 0.5). The stat's documentation lists which parameters it can accept.
The key_glyph argument of layer() may also be passed on through .... This can be one of the functions described as key glyphs, to change the display of the layer in the legend.

arrow_colour

The outline colour of the arrow segment and arrow head when using fixed arrow parameters.

arrow_head_length

A grid unit specifying the length of the arrow head (from tip to base).

arrow_neck_length

A numeric value specifying the neck length from the end of the segment to the base of the arrow head.

arrow_fill

The fill colour of the arrow head when using fixed arrow parameters and a closed arrow type.

arrow_type

One of "open" or "closed" indicating whether the arrow head should be drawn as an open or closed triangle when using fixed arrow parameters.

lineend

Line end style (round, butt, square).

linejoin

Line join style (round, mitre, bevel).

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

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. It can also be a named logical vector to finely select the aesthetics to display. To include legend keys for all levels, even when no data exists, use TRUE. If NA, all levels are shown in legend, but unobserved levels are omitted.

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. annotation_borders().

Details

Please note that geom_swim_arrow() requires a data argument and does not inherit data like other functions.

geom_swim_arrow() supports two approaches for defining arrow appearance:

By mapping the arrow aesthetic and supplying values with scale_arrow_discrete().
By supplying arrow_colour, arrow_fill, and arrow_type directly as fixed parameters.

When the arrow aesthetic is mapped, arrow appearance is controlled by scale_arrow_discrete() and takes precedence over fixed arrow parameters.

Aesthetics

geom_swim_arrow() understands the following aesthetics (required aesthetics are in bold):

y
xend
alpha
arrow
colour
group
linetype
linewidth

The arrow aesthetic is used to map discrete arrow styles via scale_arrow_discrete().

Legend behaviour

To display arrows as their own legend component, map a value to the arrow aesthetic and add scale_arrow_discrete(). If a single legend entry is desired, map a constant such as arrow = "Continuation".

Fixed versus scaled arrow styling

If the arrow aesthetic is not mapped, arrow appearance can be set directly with arrow_colour, arrow_fill, and arrow_type.

If the arrow aesthetic is mapped, arrow appearance is instead determined by scale_arrow_discrete(), and the fixed arrow parameters are used only as a fallback.

Underlying geom

geom_swim_arrow() is a wrapper for ggplot2::geom_segment() and supports much of the same functionality.

Examples

# Set up data for arrows
arrow_data <- patient_data |>
  dplyr::left_join(
    end_study_events |>
      dplyr::select(pt_id, label),
    by = "pt_id"
  ) |>
  dplyr::select(pt_id, end_time, label) |>
  dplyr::filter(.by = pt_id, end_time == max(end_time)) |>
  dplyr::filter(!is.na(label)) |>
  unique()

# Parameter-driven arrow styling
geom_swim_arrow(
  data = arrow_data,
  mapping = aes(xend = end_time, y = pt_id),
  linewidth = 0.1,
  arrow_neck_length = 5,
  arrow_head_length = grid::unit(0.25, "inches"),
  arrow_colour = "slateblue",
  arrow_fill = "cyan",
  arrow_type = "closed"
)
#> mapping: y = ~pt_id, xend = ~end_time 
#> geom_swim_arrow: arrow.fill = cyan, arrow_colour = slateblue, arrow_head_length = 0.25, arrow_neck_length = 5, arrow_type = closed, lineend = butt, linejoin = round, na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity 

# Scale-driven arrow styling with a separate legend entry
ggplot2::ggplot() +
  geom_swim_arrow(
    data = arrow_data,
    mapping = ggplot2::aes(
      xend = end_time,
      y = pt_id,
      arrow = "Continuation"
    ),
    linewidth = 0.1,
    arrow_neck_length = 5,
    arrow_head_length = grid::unit(0.25, "inches"),
    show.legend = c(arrow = TRUE)
  ) +
  scale_arrow_discrete(
    limits = "Continuation",
    colours = "slateblue",
    fills = "cyan",
    types = "closed",
    name = NULL
  )