ChordPlotAtomic: Atomic chord plot (internal)

In plotthis: High-Level Plotting Built Upon 'ggplot2' and Other Plotting Packages

Atomic chord plot (internal)

Description

Core implementation for drawing a chord diagram using circlize::chordDiagram(). This is the workhorse behind the exported ChordPlot function — it takes a single data frame (no split_by support) and returns a patchwork wrapped element.

Chord diagrams visualise relationships (flows) between two sets of categories arranged around a circle. The width of each link is proportional to the value (y) connecting its source and target nodes.

Usage

ChordPlotAtomic(
  data,
  y = NULL,
  from = NULL,
  from_sep = "_",
  to = NULL,
  to_sep = "_",
  flip = FALSE,
  links_color = c("from", "to"),
  theme = "theme_this",
  theme_args = list(),
  palette = "Paired",
  palcolor = NULL,
  palreverse = FALSE,
  alpha = 0.5,
  labels_rot = FALSE,
  title = NULL,
  subtitle = NULL,
  keep_na = FALSE,
  keep_empty = FALSE,
  ...
)

Arguments

data	A data frame.
y	A character string specifying the numeric column whose values determine link thickness. When NULL, the count of observations per (from, to) pair is used.
from	A character string (or vector) specifying the column name(s) for the source nodes. Character/factor columns are expected. Multiple columns are concatenated with from_sep.
from_sep	A character string to join multiple from columns. Default "_".
to	A character string (or vector) specifying the column name(s) for the target nodes. Character/factor columns are expected. Multiple columns are concatenated with to_sep.
to_sep	A character string to join multiple to columns. Default "_".
flip	Logical; if TRUE, swap the source and target nodes, reversing the link direction.
links_color	A character string controlling which node's colour each link ribbon takes: "from" (default) or "to".
theme	A character string or a theme class (i.e. ggplot2::theme_classic) specifying the theme to use. Default is "theme_this".
theme_args	A list of arguments to pass to the theme function.
palette	A character string specifying the palette to use. A named list or vector can be used to specify the palettes for different split_by values.
palcolor	A character string specifying the color to use in the palette. A named list can be used to specify the colors for different split_by values. If some values are missing, the values from the palette will be used (palcolor will be NULL for those values).
palreverse	A logical value indicating whether to reverse the palette. Default is FALSE.
alpha	Numeric transparency for the link ribbons (0–1). Default 0.5.
labels_rot	Logical; if TRUE, rotate sector labels by 90 degrees (clockwise). Default FALSE uses niceFacing for automatic orientation.
title	A character string specifying the title of the plot. A function can be used to generate the title based on the default title. This is useful when split_by is used and the title needs to be dynamic.
subtitle	A character string specifying the subtitle of the plot.
keep_na	A logical value or a character to replace the NA values in the data. It can also take a named list to specify different behavior for different columns. If TRUE or NA, NA values will be replaced with NA. If FALSE, NA values will be removed from the data before plotting. If a character string is provided, NA values will be replaced with the provided string. If a named vector/list is provided, the names should be the column names to apply the behavior to, and the values should be one of TRUE, FALSE, or a character string. Without a named vector/list, the behavior applies to categorical/character columns used on the plot, for example, the x, group_by, fill_by, etc.
keep_empty	One of FALSE, TRUE and "level". It can also take a named list to specify different behavior for different columns. Without a named list, the behavior applies to the categorical/character columns used on the plot, for example, the x, group_by, fill_by, etc. FALSE (default): Drop empty factor levels from the data before plotting. TRUE: Keep empty factor levels and show them as a separate category in the plot. "level": Keep empty factor levels, but do not show them in the plot. But they will be assigned colors from the palette to maintain consistency across multiple plots. Alias: levels
...	Additional arguments.

Value

A patchwork wrapped element with height and width attributes (in inches) attached. The original data is stored in the p$data field.

Architecture

1. Column resolution — from, to, and y are validated and transformed via check_columns. Multi-column from and to are concatenated with their respective separators (from_sep, to_sep).

2. Count aggregation — when y = NULL, the count of observations per (from, to) pair is computed as a new .y column. Factor levels from the original data are preserved.

3. NA / empty-level handling — process_keep_na_empty() applies keep_na and keep_empty policies.

4. Flip — when flip = TRUE, the from and to columns are swapped, effectively reversing the link direction.

5. Colour mapping — palette_this() assigns colours to all unique from and to values (the grid sectors). NA values are mapped to a literal "NA" level and assigned a colour from the palette.

6. Link colour resolution — links_color controls whether each connecting ribbon takes its colour from the "from" side (default) or the "to" side.

7. circlize rendering — two rendering paths exist, selected by labels_rot:

   • Horizontal labels (labels_rot = FALSE): track 1 has a fixed height of 1 mm and uses niceFacing = TRUE for automatic label rotation. Track 2 adds axis ticks on the outside for wide-enough sectors.

   • Rotated labels (labels_rot = TRUE): track 1 height is computed from the maximum string width of all node names, and labels are rendered with facing = "clockwise". Track 2 adds axis ticks.

   Links use arrow heads (link.arr.type = "big.arrow") and differentiated height (direction.type = c("diffHeight", "arrows")). Both tracks set bg.border = NA to prevent border lines from appearing between sectors.

8. Patchwork integration — the circlize formula is wrapped via wrap_elements() so it can be composed with other ggplot objects. Title and subtitle are added via plot_annotation().

9. Dimension attributes — height and width attributes (in inches) are set to a base size (7) scaled up by 2, 4, or 6 depending on the maximum label character width when labels_rot = TRUE.

plotthis documentation built on July 9, 2026, 5:07 p.m.