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Atomic radar/spider plot (internal)

Source: R/radarplot.R
RadarPlotAtomic.Rd

Core implementation for drawing a single radar (or spider) chart. This is the workhorse behind the exported RadarPlot and SpiderPlot functions — it takes a single data frame (no split_by support) and returns a ggplot object.

Radar charts display multivariate data on a two-dimensional polar coordinate system where each variable (x-axis category) is placed along a radial axis evenly spaced around the circle. The data values are connected by lines forming a polygon (or multiple polygons when group_by is provided). When polygon = FALSE (the default) the grid is rendered as concentric circles (classic radar chart); when polygon = TRUE straight polygonal grid lines are used (spider chart variant).

The polar coordinate system is implemented via a local coord_radar() helper that extends ggplot2::CoordPolar with is_linear = TRUE, allowing discrete x-axis positions to be mapped to evenly spaced angular coordinates.

Usage

RadarPlotAtomic(
  data,
  x,
  x_sep = "_",
  group_by = NULL,
  group_by_sep = "_",
  y = NULL,
  group_name = NULL,
  groups = NULL,
  scale_y = c("group", "global", "x", "none"),
  y_min = 0,
  y_max = NULL,
  y_nbreaks = 4,
  polygon = FALSE,
  fill = TRUE,
  linewidth = 1,
  pt_size = 4,
  max_charwidth = 16,
  bg_color = "grey80",
  bg_alpha = 0.1,
  theme = "theme_this",
  theme_args = list(),
  palette = "Paired",
  palcolor = NULL,
  palreverse = FALSE,
  facet_by = NULL,
  facet_scales = "fixed",
  facet_ncol = NULL,
  facet_nrow = NULL,
  facet_byrow = TRUE,
  alpha = 0.2,
  aspect.ratio = 1,
  legend.position = waiver(),
  legend.direction = "vertical",
  keep_na = FALSE,
  keep_empty = FALSE,
  title = NULL,
  subtitle = NULL,
  ...
)

Arguments

data

A data frame.

x

A character string specifying the column name of the data frame to plot on the x-axis (the radial categories). Must be character or factor. Multiple columns can be provided; they are concatenated with x_sep as the separator.

x_sep

A character string used to join multiple x columns. Default "_". Ignored when x is a single column.

group_by

A character vector of column names to group the data into separate filled polygons. Each unique combination becomes a distinct polygon layer. Multiple columns are concatenated with group_by_sep. When NULL, a single polygon is drawn with no legend.

group_by_sep

A character string used to join multiple group_by columns. Default "_".

y

A character string specifying the numeric column for the radial axis. When NULL, the count of observations in each (x, group_by, facet_by) combination is used.

group_name

A character string used as the colour/fill legend title. When NULL, the group_by column name is used.

groups

A character vector of group values (in the group_by column) to include in the plot. When NULL, all groups are included. This can control which groups appear and their legend order. Implies keep_empty = FALSE for the group_by column: groups not present in the data are not shown in the legend.

scale_y

How should the radial axis be scaled? Default is "group". Options are "group", "global", "x", and "none".

  • "group" — scaled to the fraction within each group.

  • "global" — scaled to the fraction of the total.

  • "x" — scaled to the fraction within each x-axis category.

  • "none" — raw counts or values, no scaling.

y_min

A numeric value setting the minimum of the radial axis. Default 0.

y_max

A numeric value setting the maximum of the radial axis. When NULL, the maximum data value is used.

y_nbreaks

A numeric value for the number of breaks (concentric grid lines) on the radial axis. Default 4.

polygon

A logical value. When TRUE, the background grid is drawn as a polygon (spider chart style); when FALSE (default), concentric circles are used (radar chart style).

fill

A logical value. When TRUE (default), the data polygons are filled with the group colour. When FALSE, only outlines are drawn.

linewidth

A numeric value for the width of the polygon outline lines. Default 1.

pt_size

A numeric value for the size of the data point markers. Default 4.

max_charwidth

A numeric value for the maximum character width of x-axis labels before wrapping. Default 16.

bg_color

A character string specifying the background fill colour. Default "grey80".

bg_alpha

A numeric value for the transparency of the background fill. Default 0.1.

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.

facet_by

A character string specifying the column name of the data frame to facet the plot. Otherwise, the data will be split by split_by and generate multiple plots and combine them into one using patchwork::wrap_plots

facet_scales

Whether to scale the axes of facets. Default is "fixed" Other options are "free", "free_x", "free_y". See ggplot2::facet_wrap

facet_ncol

A numeric value specifying the number of columns in the facet. When facet_by is a single column and facet_wrap is used.

facet_nrow

A numeric value specifying the number of rows in the facet. When facet_by is a single column and facet_wrap is used.

facet_byrow

A logical value indicating whether to fill the plots by row. Default is TRUE.

alpha

A numeric value specifying the transparency of the plot.

aspect.ratio

A numeric value specifying the aspect ratio of the plot.

legend.position

A character string specifying the position of the legend. if waiver(), for single groups, the legend will be "none", otherwise "right".

legend.direction

A character string specifying the direction of the legend.

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

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.

...

Additional arguments.

Value

A ggplot object with height and width attributes (in inches) attached.

Architecture

  1. Column resolution — x, y, group_by, and facet_by are validated and transformed via check_columns. Multi-column inputs for x and group_by are concatenated using x_sep and group_by_sep.

  2. Group setup — When group_by is NULL, a dummy .group factor is created so polygons still draw. The legend is suppressed. When groups is provided, data is filtered to only those group levels.

  3. Count aggregation — When y = NULL, the count of observations in each unique (x, group_by, facet_by) combination is computed. Factor levels are preserved after aggregation.

  4. Proportion scaling — The scale_y argument controls y-value normalisation: "group" scales within each group, "global" within each facet (or the whole dataset), "x" within each x category, and "none" leaves values raw. Percent labels are used for scaled modes.

  5. NA / empty-level handling — process_keep_na_empty() applies keep_na and keep_empty policies. Per-column keep_empty settings for x, group_by, and facet_by are extracted; facet columns must share the same value.

  6. Coordinate setup — The local coord_radar() creates a CoordPolar subclass with is_linear = TRUE, placing discrete x positions at evenly spaced angles.

  7. Y-axis range — y_min, y_max, and y_nbreaks determine the radial axis limits and the number of concentric grid lines.

  8. Colour mapping — palette_this() assigns colours to all group_by levels, including NA (defaulting to "grey80").

  9. Background layer — When polygon = TRUE, a polygonal background fills the area between y_min and y_max. When polygon = FALSE, a smooth circular background is interpolated via 360 sample points.

  10. Radial grid lines — geom_path() draws radial lines from y_min to y_max at each x-axis position, respecting facets.

  11. Polygon grid — When polygon = TRUE, concentric polygonal grid lines are drawn at each break level via geom_polygon().

  12. Data rendering — geom_polygon() draws the filled (or unfilled) polygons for each group. geom_point() adds points at each observation. Radial axis labels are rendered as text at a fixed angular offset.

  13. Scale configuration — scale_y_continuous() sets the radial axis limits and breaks. scale_x_discrete() positions the category labels. Colour scales use scale_fill_manual() and scale_color_manual() with drop controlled by keep_empty_group.

  14. Circular grid lines — When polygon = FALSE, dashed circular grid lines are styled via panel.grid.major.y.

  15. Dimension calculation — calculate_plot_dimensions() computes plot height and width from aspect.ratio, legend metrics, and a base height.

  16. Faceting — facet_plot() wraps the plot with facet_wrap / facet_grid if facet_by is supplied, respecting the keep_empty setting for facet variables.