guide_glycan: Use glycan cartoons as legend labels

In glydraw: Draw Beautiful Symbol Nomenclature for Glycans

Use glycan cartoons as legend labels

Description

guide_glycan() is a legend guide that replaces the usual text labels with glycan cartoons while retaining the legend keys drawn by the plot layers. Mapped discrete values and values returned by the scale's labels argument may be glycan structure strings supported by glyparse::auto_parse() or glyrepr::glycan_structure() vectors.

Usage

guide_glycan(
  title = ggplot2::waiver(),
  theme = NULL,
  position = NULL,
  direction = NULL,
  override.aes = list(),
  nrow = NULL,
  ncol = NULL,
  reverse = FALSE,
  order = 0,
  size = 0.4,
  orient = c("H", "V"),
  hjust = 0,
  vjust = vjust_red_end(),
  show_linkage = TRUE,
  red_end = "",
  fuc_orient = c("flex", "up"),
  edge_linewidth = 0.8,
  node_linewidth = 0.8,
  node_size = 1,
  colors = NULL,
  style = NULL
)

Arguments

title	A character string or expression indicating a title of guide. If NULL, the title is not shown. By default (waiver()), the name of the scale object or the name specified in labs() is used for the title.
theme	A theme object to style the guide individually or differently from the plot's theme settings. The theme argument in the guide partially overrides, and is combined with, the plot's theme. Arguments that apply to a single legend are respected, most of which have the legend-prefix. Arguments that apply to combined legends (the legend box) are ignored, including legend.position, ⁠legend.justification.*⁠, legend.location and ⁠legend.box.*⁠.
position	A character string indicating where the legend should be placed relative to the plot panels. One of "top", "right", "bottom", "left", or "inside".
direction	A character string indicating the direction of the guide. One of "horizontal" or "vertical".
override.aes	A list specifying aesthetic parameters of legend key. See details and examples.
nrow, ncol	The desired number of rows and column of legends respectively.
reverse	logical. If TRUE the order of legends is reversed.
order	positive integer less than 99 that specifies the order of this guide among multiple guides. This controls the order in which multiple guides are displayed, not the contents of the guide itself. If 0 (default), the order is determined by a secret algorithm.
size	Positive scalar that uniformly scales each legend-label cartoon. Defaults to 0.4.
orient	Glycan drawing orientation, either "H" for horizontal or "V" for vertical. Defaults to "H".
hjust	Horizontal cartoon justification between 0 and 1, or hjust_red_end(). It defaults to 0 for horizontal cartoons and hjust_red_end() for vertical cartoons.
vjust	Vertical cartoon justification between 0 and 1, or vjust_red_end(). It defaults to vjust_red_end() for horizontal cartoons and 0.5 for vertical cartoons.
show_linkage	Whether to show glycosidic linkage annotations inside the cartoons. Defaults to TRUE.
red_end	Reducing-end annotation passed to glycanGrob(). Use "~" for a wave, or another string to display that text. Defaults to "".
fuc_orient	Fuc-like triangle orientation passed to glycanGrob().
edge_linewidth	Linkage linewidth passed to glycanGrob().
node_linewidth	Node-border linewidth passed to glycanGrob().
node_size	Node-size multiplier passed to glycanGrob().
colors	Optional named character vector of monosaccharide fill colors passed to glycanGrob().
style	A glydraw_style object that supplies rendering options. Explicitly supplied rendering arguments override it.

Value

A ggplot2 legend guide that draws glycan cartoons in place of text labels.

Examples

glycans <- data.frame(
  structure = c(
    "Gal(b1-3)GalNAc(a1-",
    "Man(a1-3)[Man(a1-6)]Man(b1-4)GlcNAc(b1-"
  ),
  abundance = c(12, 8)
)

ggplot2::ggplot(
  glycans,
  ggplot2::aes(
    x = .data$structure,
    y = .data$abundance,
    fill = .data$structure
  )
) +
  ggplot2::geom_col() +
  ggplot2::scale_fill_discrete(guide = guide_glycan())

glydraw documentation built on July 25, 2026, 9:06 a.m.