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Atomic dot/lollipop plot

Source: R/dotplot.R
DotPlotAtomic.Rd

Core implementation for dot plots and lollipop plots. This is the internal workhorse dispatched by both DotPlot() and LollipopPlot(). It renders a matrix of points where dot size encodes one variable and dot fill colour encodes another, with optional background stripes and a lollipop (bar + dot) display mode.

Usage

DotPlotAtomic(
  data,
  x,
  y,
  x_sep = "_",
  y_sep = "_",
  flip = FALSE,
  lollipop = FALSE,
  size_by = NULL,
  fill_by = NULL,
  fill_cutoff = NULL,
  palreverse = FALSE,
  size_name = NULL,
  fill_name = NULL,
  fill_cutoff_name = NULL,
  size_min = 1,
  size_max = 10,
  theme = "theme_this",
  theme_args = list(),
  palette = "Spectral",
  palcolor = NULL,
  alpha = 1,
  border_color = "black",
  border_size = 0.5,
  border_alpha = 1,
  lower_quantile = 0,
  upper_quantile = 0.99,
  lower_cutoff = NULL,
  upper_cutoff = NULL,
  facet_by = NULL,
  facet_scales = "fixed",
  facet_ncol = NULL,
  facet_nrow = NULL,
  facet_byrow = TRUE,
  x_text_angle = 0,
  aspect.ratio = 1,
  legend.position = "right",
  legend.direction = "vertical",
  add_bg = FALSE,
  bg_palette = "stripe",
  bg_palcolor = NULL,
  bg_alpha = 0.2,
  bg_direction = c("vertical", "horizontal", "v", "h"),
  title = NULL,
  subtitle = NULL,
  xlab = NULL,
  ylab = NULL,
  keep_na = FALSE,
  keep_empty = FALSE,
  ...
)

Arguments

data

A data frame.

x

A character vector specifying the column(s) to use for the x-axis. Can be numeric (for scatter/lollipop mode) or factor/character (for dot matrix mode). When multiple columns are provided for a non-numeric axis, they are concatenated with x_sep as the separator.

y

A character vector specifying the column(s) to use for the y-axis. Can be numeric (for scatter mode) or factor/character (for dot matrix or lollipop mode). When multiple columns are provided for a non-numeric axis, they are concatenated with y_sep as the separator.

x_sep

A character string used to join multiple x column values into a single factor level. Only used when x is non-numeric and multiple columns are provided. Default: "_".

y_sep

A character string used to join multiple y column values into a single factor level. Only used when y is non-numeric and multiple columns are provided. Default: "_".

flip

A logical value. If TRUE, the x and y axes are swapped via coord_flip(). Dimension calculation accounts for the flip. Default: FALSE.

lollipop

A logical value. If TRUE, renders a lollipop plot with bars extending from x = 0 to each data point, capped by filled dots. Requires x to be numeric and y to be factor/character. Default: FALSE.

size_by

A character string naming a numeric column whose values control dot size. When NULL (the default), the per-combination observation count is computed automatically (via dplyr::summarise(n = n())) and used as the size variable. If fill_by is also present, the first value of fill_by per combination is retained with a warning. A single numeric value is also accepted and sets a constant dot size (used by ScatterPlot).

fill_by

A character string naming a numeric column whose values control the fill colour of the dots (and lollipop inner bars). A continuous gradient from palette is applied via scale_fill_gradientn(). When NULL (the default), all dots are filled with a single constant colour from the middle of the palette.

fill_cutoff

A string expression specifying which values of fill_by to grey out. Format: an operator followed by a number, e.g. "< 18", "<= 18", "> 18", or ">= 18". Values matching the condition are set to NA and rendered in grey ("grey80"), while the rest are coloured by the fill gradient. The operator determines which side of the threshold is greyed out, independent of palreverse. A numeric value is also accepted as shorthand for "<" (e.g. 18 is equivalent to "< 18"). Requires fill_by to be set.

palreverse

A logical value indicating whether to reverse the palette. Default is FALSE.

size_name

A character string for the size legend title. When NULL (the default), the size_by column name is used.

fill_name

A character string for the fill colour-bar legend title. When NULL (the default), the fill_by column name is used.

fill_cutoff_name

A character string for the fill cutoff legend title (shown when fill_cutoff is active). Defaults to "<fill_by> <fill_cutoff>", e.g. "mpg < 18".

size_min

A numeric value for the smallest dot size in the scale_size(range = c(size_min, size_max)) range. Default: 1.

size_max

A numeric value for the largest dot size in the scale_size(range = c(size_min, size_max)) range. Default: 10.

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).

alpha

A numeric value specifying the transparency of the plot.

border_color

Controls the dot border colour and lollipop outer-shadow appearance:

  • TRUE — dot borders and lollipop inner bars follow the fill_by gradient via scale_color_gradientn(); lollipop outer shadow is black.

  • "black" (default) — constant black borders on dots and black outer shadow on lollipop bars.

  • A colour string (e.g. "red", "#FF0000") — constant colour for both dot borders and lollipop outer shadows.

  • FALSE — no dot borders and no lollipop outer shadow (the inner coloured bars remain visible in lollipop mode).

border_size

A numeric value for the stroke width of dot borders and the base linewidth of lollipop bars. In lollipop mode, the outer shadow uses border_size * 4 and the inner bar uses border_size * 2. Default: 0.5.

border_alpha

A numeric value in [0, 1] controlling the transparency of dot borders and lollipop bar segments. Default: 1.

lower_quantile, upper_quantile

Lower and upper quantiles for the continuous color/fill scale. The actual cutoffs are determined by these quantiles when lower_cutoff and upper_cutoff are NULL. Defaults: lower_quantile = 0, upper_quantile = 0.99.

lower_cutoff, upper_cutoff

Explicit lower and upper cutoffs for the continuous color/fill scale. When NULL (the default), the cutoffs are determined by lower_quantile and upper_quantile via quantile. Values outside the [lower_cutoff, upper_cutoff] range are clamped (winsorized) to the nearest cutoff value.

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.

add_bg

A logical value. If TRUE, alternating background stripes are drawn behind the points via bg_layer(). The striped axis is determined by bg_direction. Requires the striped axis to be non-numeric. Default: FALSE.

bg_palette

A character string specifying the palette for the background stripe colours. Passed to bg_layer(). Default: "stripe".

bg_palcolor

A character vector of colours for the background stripes. Passed to bg_layer(). When NULL (default), colours are derived from bg_palette.

bg_alpha

A numeric value in [0, 1] for the transparency of the background stripes. Default: 0.2.

bg_direction

A character string specifying which axis receives the alternating background stripes. "vertical" (default) stripes by x levels; "horizontal" stripes by y levels. Abbreviations "v" and "h" are also accepted.

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.

Details

The function supports two display modes:

  • Dot plot (lollipop = FALSE, the default) — renders ggplot2::geom_point() with shape = 21 (filled circle). Either or both axes can be numeric (producing a scatter plot) or factor (producing a dot matrix). Dot size scales by size_by (or the per-combination observation count when size_by is NULL) via scale_size(range = c(size_min, size_max)). Dot fill follows the fill_by column via scale_fill_gradientn().

  • Lollipop plot (lollipop = TRUE) — expects a numeric x and a factor/character y. Renders a two-layer bar: an outer shadow segment followed by an inner coloured segment, each capped by a filled dot. The outer shadow is black (or a custom colour when border_color is a string), and the inner segment + dot fill follow fill_by.

When add_bg = TRUE, alternating background stripes are drawn via bg_layer() along the discrete axis (vertical stripes for factor x, horizontal stripes for factor y). The fill colour scale is prepared via prepare_continuous_color_scale() and can be trimmed with lower_quantile/upper_quantile or lower_cutoff/upper_cutoff.

When fill_cutoff is set (e.g. "< 18"), values of fill_by matching the condition are set to NA and rendered in grey ("grey80"), with a separate legend entry documenting the cutoff.

Border colour modes:

  • border_color = TRUE — dot borders and lollipop inner bar colour track the fill_by gradient via scale_color_gradientn(); lollipop outer shadow is black.

  • border_color = "black" (default) — constant black borders on dots and a black outer shadow on lollipop bars.

  • border_color = FALSE — no dot borders, no lollipop outer shadow (the inner coloured segment remains).

Architecture

DotPlotAtomic executes the following steps:

  1. ggplot dispatch — selects gglogger::ggplot or ggplot2::ggplot based on getOption("plotthis.gglogger.enabled").

  2. bg_direction normalisation — match.arg() resolves "v"/"h" abbreviations to "vertical"/"horizontal".

  3. Axis type detection — determines whether x (resp. y) is numeric by checking that the column is a single name and the data column is neither character nor factor.

  4. Column resolution — non-numeric x and y are processed via check_columns() with force_factor = TRUE, allow_multi = TRUE, concat_multi = TRUE using x_sep/y_sep. fill_by and facet_by are also validated.

  5. NA / empty handling — process_keep_na_empty() filters data and extracts keep_empty settings for x, y, and facet_by.

  6. Multi-facet keep_empty guard — when facet_by has more than one column, the keep_empty values must be identical for all facet columns (consistent drop behaviour).

  7. fill_cutoff guard — errors if fill_cutoff is set but fill_by is NULL.

  8. Size-by resolution — when size_by = NULL:

    • Groups data by the unique combination of x, y, and facet_by columns and counts rows per combination into .size.

    • If fill_by is present, summarise() also takes the first value of fill_by per group (with a warning that only the first value is used).

    • Factor levels of x, y, and facet_by are preserved post-summary.

    • Sets size_by <- ".size".

  9. fill_cutoff parsing — if fill_cutoff is set:

    • Numeric shorthand (e.g. 18) is converted to "< 18".

    • The string is parsed with regex ^(<=?|>=?)\\s*(-?[0-9.]+)$ to extract operator and numeric threshold.

    • A switch() on the operator NAs-out matching values in fill_by (e.g. "<" sets values below the threshold to NA).

    • A label "<fill_by> <fill_cutoff>" is generated for the legend.

  10. Default fill_by — when fill_by = NULL, a synthetic .fill_by column (constant 1) is created and the fill legend is suppressed.

  11. Continuous colour scale preparation — when fill_by is numeric, prepare_continuous_color_scale() computes feat_colors_value (the range endpoints after optional quantile trimming or cutoff clamping).

  12. Base ggplot — initialises ggplot(data, aes(x, y)).

  13. Background layer — if add_bg = TRUE:

    • Vertical stripes (bg_direction = "vertical") require a non-numeric x-axis; horizontal stripes require a non-numeric y-axis.

    • Calls bg_layer() with the relevant discrete column and stripe styling.

  14. Discrete axis scales — scale_x_discrete() / scale_y_discrete() with drop = !isTRUE(keep_empty_*) for non-numeric axes.

  15. Lollipop branch (lollipop = TRUE):

    • Sets x-axis expansion to c(0, 0, 0.05, 0) (bars start at x = 0 with a 5\

    • Outer shadow — geom_segment() from x = 0 to the data value, coloured black (or border_color when a string), with linewidth border_size * 4. Skipped when border_color = FALSE.

    • Inner coloured bar — geom_segment() mapped to the fill_by gradient via scale_color_gradientn(), with linewidth border_size * 2.

    • ggnewscale::new_scale_color() resets the colour scale for the subsequent point layer.

  16. Point layer — geom_point(shape = 21) (filled circle with border) with four dispatch paths:

    • Numeric size + gradient border: aes(fill, color) both mapped to fill_by; size = size_by constant.

    • Numeric size + constant/no border: aes(fill, color = "") with a constant colour string.

    • Column size + gradient border: aes(size, fill, color) with scale_size(range = c(size_min, size_max)) and a size legend (title = size_name, order = 1).

    • Column size + constant/no border: aes(size, fill, color = "") with the same size scale.

  17. Fill scale — scale_fill_gradientn() with palette_this(), feat_colors_value for rescaled colour mapping, na.value = "grey80", and a colour-bar legend (title = fill_name, order = 2) or guide_none() when no fill_by was provided.

  18. Labels — labs(title, subtitle, x, y) with fallback to column names via %||%.

  19. Theme — do_call(theme, theme_args) plus panel.grid.major (grey80 dashed) and rotated x-axis text via calc_just(x_text_angle).

  20. Colour (border) scale:

    • border_color = TRUE — scale_color_gradientn() following the fill_by gradient (with border_alpha), guide suppressed (the fill colour-bar serves both).

    • border_color = FALSE — scale_color_manual() with "transparent", guide suppressed.

    • Constant string — scale_color_manual() with the alpha-adjusted colour, guide suppressed.

  21. fill_cutoff legend — when fill_cutoff is active and there are NA values in fill_by, a guide_legend() (order = 3) is added showing the cutoff label with a grey fill and the border colour.

  22. Flip — optional coord_flip() swaps x and y axes.

  23. Dimension calculation — calculate_plot_dimensions() with base_height = 4.5, aspect.ratio = NULL, and per-axis scale factors (0.9 for the categorical axis driving width, 0.6 for the categorical axis driving height). Legend width, y-axis label length, and minimum dimensions (width \(\ge\) 5, height \(\ge\) 4) are factored in. A fallback manual calculation is used when calculate_plot_dimensions() returns NULL.

  24. Faceting — facet_plot() applies facet_grid/facet_wrap with drop = !isTRUE(keep_empty_facet).