Atomic area plot (internal) — AreaPlotAtomic • plotthis

Core implementation for drawing a single stacked area plot. This is the workhorse behind the exported AreaPlot function — it takes a single data frame (no split_by support) and returns a ggplot object. The plot shows how one or more groups' numeric values (or counts) accumulate across a discrete x-axis, with each group rendered as a filled area stacked from baseline.

Usage

AreaPlotAtomic(
  data,
  x,
  y = NULL,
  x_sep = "_",
  group_by = NULL,
  group_by_sep = "_",
  group_name = NULL,
  scale_y = FALSE,
  theme = "theme_this",
  theme_args = list(),
  palette = "Paired",
  palcolor = NULL,
  palreverse = FALSE,
  alpha = 1,
  facet_by = NULL,
  facet_scales = "fixed",
  facet_ncol = NULL,
  facet_nrow = NULL,
  facet_byrow = TRUE,
  x_text_angle = 0,
  aspect.ratio = 1,
  legend.position = waiver(),
  legend.direction = "vertical",
  title = NULL,
  subtitle = NULL,
  xlab = NULL,
  ylab = NULL,
  keep_na = FALSE,
  keep_empty = FALSE,
  ...
)

Arguments

data

A data frame.

x

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

y

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

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 fill the areas by. Each unique combination becomes a separate stacked area. Multiple columns are concatenated with group_by_sep. When NULL, a single filled area is drawn (no grouping) and the legend is hidden.

group_by_sep

A character string to separate concatenated group_by columns. Default "_".

group_name

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

scale_y

A logical value. When TRUE, y-values are scaled to proportions within each (x, facet_by) group so that each x position stacks to 1.0. The y-axis labels switch from numeric to percent format automatically.

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

A numeric value specifying the transparency of the plot.

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.

x_text_angle

A numeric value specifying the angle of the x-axis text.

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.

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.

xlab

A character string specifying the x-axis label.

ylab

A character string specifying the y-axis label.

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

Architecture

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 into single columns using their respective separators (x_sep, group_by_sep).
NA / empty-level handling — process_keep_na_empty() applies keep_na and keep_empty policies. Per-column keep_empty settings are extracted for x, group_by, and facet_by independently. The facet columns must have identical keep_empty values.
Count aggregation — when y = NULL, the count of observations in each unique (x, group_by, facet_by) combination is computed as a new .count column. Factor levels are preserved after aggregation.
Proportion scaling — when scale_y = TRUE, the y-values are divided by the sum within each (x, facet_by) group, producing a proportion (0–1). Percent labels are used automatically on the y-axis.
Empty-fill guard — when group_by = NULL (no grouping), a dummy .fill factor is created so the single area still draws with the first palette colour. The legend is suppressed (legend.position = "none").
Colour mapping — palette_this() assigns colours to all group_by levels, including NA (defaulting to "grey80").
Data completion — complete() pads all x × group_by (× facet_by) combinations with y = 0. This prevents geom_area() from interpolating across missing groups, which would otherwise cause stacked areas to exceed the correct total.
x-axis numeric mapping — the discrete x variable is converted to a numeric position column (.x_numeric) so geom_area() can draw continuous area fills between x positions. NA levels are placed at position n_levels + 1.
Plot assembly — the ggplot object is built with geom_area(position = position_stack(vjust = 0.5)), scale_x_discrete() (breaks from factor levels), scale_y_continuous() (percent labels when scaled), and scale_fill_manual() with per-group colours. The fill scale drop argument is controlled by keep_empty_group.
Dimension calculation — calculate_plot_dimensions() computes plot height and width from the x-axis category count, aspect.ratio, and legend metrics. The resulting height / width attributes are stored on the ggplot object.
Faceting — facet_plot() wraps the plot with facet_wrap / facet_grid if facet_by is provided, respecting the keep_empty setting for facet variables.