barplot: Bar / SplitBar / Waterfall Plot

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

Bar / SplitBar / Waterfall Plot

Description

BarPlot draws bar plots with flexible fill, grouping, labelling, and annotation options. Supports both simple single-colour bars and grouped bars (dodged or stacked). Bars can be filled by a categorical variable (discrete colour scale), a continuous variable (colour gradient), or a fixed colour.

The function supports count aggregation (omit y to plot observation counts), proportion scaling (scale_y = TRUE for grouped bars), background stripes (add_bg), bar labels, trend lines, horizontal reference lines, and splitting into separate sub-plots via split_by.

SplitBarPlot (also known as WaterfallPlot) draws a divergent bar plot where bars extend left (negative values) and right (positive values) from a central zero line. The bar fill colour and opacity can encode additional variables, and the vertical ordering of categories is fully customisable.

The function supports split_by to produce separate panels, facet_by for grouped views within panels, and alpha_by for encoding a secondary numeric variable via opacity.

Usage

BarPlot(
  data,
  x,
  x_sep = "_",
  y = NULL,
  flip = FALSE,
  fill_by = TRUE,
  fill_name = NULL,
  line_name = NULL,
  label_nudge = 0.02,
  label = NULL,
  label_fg = "black",
  label_size = 4,
  label_bg = "white",
  label_bg_r = 0.1,
  group_by = NULL,
  group_by_sep = "_",
  group_name = NULL,
  split_by = NULL,
  split_by_sep = "_",
  facet_by = NULL,
  facet_scales = "fixed",
  facet_ncol = NULL,
  facet_nrow = NULL,
  facet_byrow = TRUE,
  facet_args = list(),
  add_bg = FALSE,
  bg_palette = "stripe",
  bg_palcolor = NULL,
  bg_alpha = 0.2,
  add_line = NULL,
  line_color = "red2",
  line_width = 0.6,
  line_type = 2,
  add_trend = FALSE,
  trend_color = "black",
  trend_linewidth = 1,
  trend_ptsize = 2,
  theme = "theme_this",
  theme_args = list(),
  palette = NULL,
  palcolor = NULL,
  palreverse = FALSE,
  alpha = 1,
  lower_quantile = 0,
  upper_quantile = 0.99,
  lower_cutoff = NULL,
  upper_cutoff = NULL,
  x_text_angle = 0,
  aspect.ratio = 1,
  y_min = NULL,
  y_max = NULL,
  position = "auto",
  position_dodge_preserve = "total",
  legend.position = "right",
  legend.direction = "vertical",
  title = NULL,
  subtitle = NULL,
  xlab = NULL,
  ylab = NULL,
  keep_empty = FALSE,
  keep_na = FALSE,
  expand = waiver(),
  width = waiver(),
  combine = TRUE,
  nrow = NULL,
  ncol = NULL,
  byrow = TRUE,
  seed = 8525,
  axes = NULL,
  axis_titles = axes,
  guides = NULL,
  design = NULL,
  ...
)

SplitBarPlot(
  data,
  x,
  y,
  y_sep = "_",
  flip = FALSE,
  split_by = NULL,
  split_by_sep = "_",
  alpha_by = NULL,
  alpha_reverse = FALSE,
  alpha_name = NULL,
  order_y = list(`+` = c("x_desc", "alpha_desc"), `-` = c("x_desc", "alpha_asc")),
  bar_height = 0.9,
  lineheight = 0.5,
  max_charwidth = 80,
  fill_by = NULL,
  fill_by_sep = "_",
  fill_name = NULL,
  direction_name = "direction",
  direction_pos_name = "positive",
  direction_neg_name = "negative",
  theme = "theme_this",
  theme_args = list(),
  palette = "Spectral",
  palcolor = NULL,
  palreverse = FALSE,
  lower_quantile = 0,
  upper_quantile = 0.99,
  lower_cutoff = NULL,
  upper_cutoff = NULL,
  facet_by = NULL,
  facet_scales = "free_y",
  facet_nrow = NULL,
  facet_ncol = NULL,
  facet_byrow = TRUE,
  aspect.ratio = 1,
  x_min = NULL,
  x_max = NULL,
  legend.position = "right",
  legend.direction = "vertical",
  title = NULL,
  subtitle = NULL,
  xlab = NULL,
  ylab = NULL,
  keep_empty = FALSE,
  keep_na = FALSE,
  combine = TRUE,
  nrow = NULL,
  ncol = NULL,
  byrow = TRUE,
  seed = 8525,
  axes = NULL,
  axis_titles = axes,
  guides = NULL,
  design = NULL,
  ...
)

WaterfallPlot(
  data,
  x,
  y,
  y_sep = "_",
  flip = FALSE,
  split_by = NULL,
  split_by_sep = "_",
  alpha_by = NULL,
  alpha_reverse = FALSE,
  alpha_name = NULL,
  order_y = list(`+` = c("x_desc", "alpha_desc"), `-` = c("x_desc", "alpha_asc")),
  bar_height = 0.9,
  lineheight = 0.5,
  max_charwidth = 80,
  fill_by = NULL,
  fill_by_sep = "_",
  fill_name = NULL,
  direction_name = "direction",
  direction_pos_name = "positive",
  direction_neg_name = "negative",
  theme = "theme_this",
  theme_args = list(),
  palette = "Spectral",
  palcolor = NULL,
  palreverse = FALSE,
  lower_quantile = 0,
  upper_quantile = 0.99,
  lower_cutoff = NULL,
  upper_cutoff = NULL,
  facet_by = NULL,
  facet_scales = "free_y",
  facet_nrow = NULL,
  facet_ncol = NULL,
  facet_byrow = TRUE,
  aspect.ratio = 1,
  x_min = NULL,
  x_max = NULL,
  legend.position = "right",
  legend.direction = "vertical",
  title = NULL,
  subtitle = NULL,
  xlab = NULL,
  ylab = NULL,
  keep_empty = FALSE,
  keep_na = FALSE,
  combine = TRUE,
  nrow = NULL,
  ncol = NULL,
  byrow = TRUE,
  seed = 8525,
  axes = NULL,
  axis_titles = axes,
  guides = NULL,
  design = NULL,
  ...
)

Arguments

data	A data frame.
x	A character string specifying the column name of the data frame to plot for the x-axis.
x_sep	A character string to join multiple x columns. Default "_".
y	A character string specifying the column name of the data frame to plot for the y-axis.
flip	Logical; if TRUE, swap the x and y axes.
fill_by	A variable used to fill the bars. Both categorical and numeric columns are accepted: TRUE (default) — fill by the x-axis values. FALSE — solid fill (first palette colour). A column name (character/factor) — discrete colour scale. A column name (numeric) — continuous gradient with quantile / cutoff controls. Ignored when group_by is provided (fill is determined by group_by).
fill_name	A character string for the fill legend title. Only applies when group_by = NULL and the fill is from fill_by.
line_name	Legend name for the reference line.
label_nudge	A numeric value controlling the distance between labels and the bar top, expressed as a fraction of the data range.
label	A column name (or TRUE) for text labels on bars. When TRUE, the y-axis values are labelled. When a column name, the values in that column are used.
label_fg	A character string specifying the label text colour.
label_size	A numeric value specifying the label text size.
label_bg	A character string specifying the label background colour.
label_bg_r	A numeric value specifying the label background corner radius.
group_by	Columns to group the data for plotting For those plotting functions that do not support multiple groups, They will be concatenated into one column, using group_by_sep as the separator
group_by_sep	The separator for multiple group_by columns. See group_by
group_name	A character string for the group fill legend title. When NULL, the group_by column name is used.
split_by	The column(s) to split the data by for separate sub-plots.
split_by_sep	Separator for concatenated split_by columns.
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.
facet_args	A list of additional arguments passed to the faceting function (e.g., scales, labeller).
add_bg	Logical; add alternating background stripes behind the bars.
bg_palette	Palette for the background stripes.
bg_palcolor	Custom colours for the background stripes.
bg_alpha	Alpha transparency for the background stripes.
add_line	A numeric y-intercept for a horizontal reference line.
line_color	Colour of the reference line.
line_width	Width of the reference line.
line_type	Linetype of the reference line (e.g., 1 = solid, 2 = dashed).
add_trend	Logical; add a trend line and points connecting the bar tops.
trend_color	Colour of the trend line.
trend_linewidth	Width of the trend line.
trend_ptsize	Size of the trend line points.
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.
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.
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.
y_min, y_max	Numeric limits for the y-axis (or x-axis when flipped).
position	A character string specifying the bar layout: "auto" (default: dodge when \le5 groups, stack otherwise), "dodge" (side-by-side), or "stack" (stacked on top of each other).
position_dodge_preserve	A character string passed to position_dodge2(): "total" preserves the overall bar group width; "single" preserves individual bar widths.
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_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
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.
expand	The values to expand the x and y axes. It is like CSS padding. When a single value is provided, it is used for both axes on both sides. When two values are provided, the first value is used for the top/bottom side and the second value is used for the left/right side. When three values are provided, the first value is used for the top side, the second value is used for the left/right side, and the third value is used for the bottom side. When four values are provided, the values are used for the top, right, bottom, and left sides, respectively. You can also use a named vector to specify the values for each side. When the axis is discrete, the values will be applied as 'add' to the 'expansion' function. When the axis is continuous, the values will be applied as 'mult' to the 'expansion' function. See also https://ggplot2.tidyverse.org/reference/expansion.html
width	A numeric value specifying the bar width (0–1).
combine	Logical; when TRUE (default), returns a combined patchwork object. When FALSE, returns a named list of ggplot objects.
ncol, nrow	Integer number of columns / rows for the combined layout.
byrow	Logical; fill the combined layout by row (default TRUE).
seed	A numeric seed for reproducibility.
axes, axis_titles	Character strings for axis handling in the combined layout.
guides	Character string for legend collection across panels.
design	A custom layout design for the combined plot.
...	Additional arguments.
y_sep	A character string to join multiple y columns. Default "_".
alpha_by	A character string naming a numeric column to encode as bar opacity. Default NULL (all bars fully opaque).
alpha_reverse	Logical; if TRUE, reverse the alpha scale direction (solid for low values, transparent for high).
alpha_name	A character string for the alpha legend title.
order_y	A named list controlling the vertical ordering of bars. Keys are "+" (positive bars), "-" (negative bars), or "*" (all bars). Values are character vectors of ordering criteria: "x_asc", "x_desc", "alpha_asc", "alpha_desc". Default orders positive bars by descending x and descending alpha; negative bars by descending x and ascending alpha.
bar_height	A numeric value (0–1) specifying the bar height as a fraction of the available category slot.
lineheight	A numeric value controlling the line height of wrapped category labels.
max_charwidth	An integer specifying the maximum character width for wrapping category labels.
fill_by_sep	A character string to join multiple fill_by columns. Default "_".
direction_name	A character string naming the internal direction column (used in legends). Default "direction".
direction_pos_name	A character string labelling the positive direction in the legend. Default "positive".
direction_neg_name	A character string labelling the negative direction in the legend. Default "negative".
x_min, x_max	Numeric limits for the x-axis. When NULL, symmetric limits are computed from the maximum absolute x-value.

Value

A ggplot object, a patchwork object, or a named list of ggplot objects (when combine = FALSE), each with height and width attributes in inches.

A ggplot object, a patchwork object, or a named list of ggplot objects (when combine = FALSE), each with height and width attributes in inches.

split_by workflow

When split_by is provided:

1. check_keep_na() and check_keep_empty() normalise the keep_na / keep_empty arguments for all columns (x, split_by, facet_by, group_by).

2. The split_by column is validated and its NA / empty levels are processed. It is then removed from the per-column keep_na / keep_empty lists.

3. The data is split by split_by (preserving level order). If split_by is NULL, the data is wrapped in a single-element list with name "...".

4. Per-split palette, palcolor, legend.position, and legend.direction are resolved via check_palette(), check_palcolor(), and check_legend().

5. BarPlotAtomic() is called for each split.

6. Results are combined via combine_plots() (when combine = TRUE) or returned as a named list.

When split_by is provided:

1. check_keep_na() and check_keep_empty() normalise the keep_na / keep_empty arguments.

2. The split_by column is validated and its NA / empty levels are processed. It is then removed from the per-column lists.

3. The data is split by split_by (preserving level order).

4. Per-split palette, palcolor, legend.position, and legend.direction are resolved.

5. SplitBarPlotAtomic() is called for each split. When title is a function, it receives the split level name for dynamic title generation.

6. Results are combined via combine_plots().

Examples

data <- data.frame(
    x = c("A", "B", "C", "D", "E", "F", "G", "H"),
    y = c(10, 8, 16, 4, 6, 12, 14, 2),
    group = c("G1", "G1", "G2", "G2", "G3", "G3", "G4", "G4"),
    facet = c("F1", "F2", "F3", "F4", "F1", "F2", "F3", "F4")
)

# Single-colour bars
BarPlot(data, x = "x", y = "y")

# Solid fill (no colour mapping)
BarPlot(data, x = "x", y = "y", fill_by = FALSE)

# Label bar tops
BarPlot(data, x = "x", y = "y", label = TRUE)
BarPlot(data, x = "x", y = "y", label = "facet", label_nudge = 0)

# Grouped bars
BarPlot(data, x = "group", y = "y", group_by = "x")

# Dodged bars with background stripes
BarPlot(data,
    x = "group", y = "y", group_by = "x",
    position = "dodge", add_bg = TRUE)

# split_by with faceting
BarPlot(data,
    x = "x", y = "y", split_by = "group",
    facet_by = "facet", position = "dodge", facet_ncol = 1)

# split_by with collected guides
BarPlot(data,
    x = "x", y = "y", split_by = "group", facet_by = "facet",
    position = "dodge", facet_ncol = 1, guides = 'collect')

# Per-split palettes
BarPlot(data,
    x = "x", y = "y", split_by = "group",
    palette = list(G1 = "Reds", G2 = "Blues", G3 = "Greens", G4 = "Purp"),
    facet_by = "facet", position = "dodge", facet_ncol = 1)

# Background stripe palette
BarPlot(data,
    x = "group", y = "y", group_by = "x",
    position = "dodge", add_bg = TRUE, bg_palette = "Spectral")

# Count bars (y = NULL)
BarPlot(data, x = "group", ylab = "count")

# Flipped axes
BarPlot(data, x = "group", flip = TRUE, ylab = "count")

# Numeric fill_by with colour gradient
BarPlot(data, x = "x", y = "y", fill_by = "y", flip = TRUE)

# Control fill colour scale limits (quantile)
BarPlot(data, x = "x", y = "y", fill_by = "y", flip = TRUE,
        lower_quantile = 0.1, upper_quantile = 0.9)

# Control fill colour scale limits (explicit cutoff)
BarPlot(data, x = "x", y = "y", fill_by = "y", flip = TRUE,
        lower_cutoff = 5, upper_cutoff = 12)

# keep_na and keep_empty examples
data <- data.frame(
    x = factor(c("A", "B", "C", "D", "E", "F", NA, "H"),
               levels = LETTERS[1:10]),
    y = c(10, 8, 16, 4, 6, NA, 14, 2),
    group = factor(c("G1", "G1", "G2", NA, "G3", "G3", "G5", "G5"),
                   levels = c("G1", "G2", "G3", "G4", "G5")),
    facet = factor(c("F1", NA, "F3", "F4", "F1", "F2", "F3", "F4"),
                   levels = c("F1", "F2", "F3", "F4", "F5"))
)

# Default: NA and empty levels dropped
BarPlot(data, x = "x", y = "y")

# Keep both NA and empty levels
BarPlot(data, x = "x", y = "y",
        keep_na = TRUE, keep_empty = TRUE)

# With faceting
BarPlot(data, x = "x", y = "y",
        keep_na = TRUE, keep_empty = TRUE, facet_by = "facet")

# Keep NA, hide empty levels but reserve their colours
BarPlot(data, x = "x", y = "y",
        keep_na = TRUE, keep_empty = 'level')

# Per-column keep_na / keep_empty
BarPlot(data, x = "x", y = "y",
        keep_na = list(x = TRUE), keep_empty = list(x = FALSE))

# Grouped bars with keep_na / keep_empty
BarPlot(data, x = "group", y = "y", group_by = "x")
BarPlot(data, x = "group", y = "y", group_by = "x",
        keep_na = TRUE, keep_empty = TRUE)
BarPlot(data, x = "group", y = "y", group_by = "x",
        keep_na = TRUE, keep_empty = TRUE, facet_by = "facet")

# Per-column on grouped bars
BarPlot(data, x = "group", y = "y", group_by = "x",
        keep_na = list(x = TRUE, group = FALSE),
        keep_empty = list(x = FALSE, group = TRUE))


set.seed(8525)
data <- data.frame(
    word = c("apple", "banana", "cherry", "date", "elderberry",
             "It is a very long term with a lot of words"),
    count = c(-10, 20, -30, 40, 50, 34),
    score = c(1, 2, 3, 4, 5, 3.2),
    group = c("A", "A", "B", "B", "C", "C")
)

# Basic split bar plot with alpha encoding
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score")

# Control label wrapping
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score",
             max_charwidth = 30, lineheight = 1.1)

# Fill by categorical variable
SplitBarPlot(data, x = "count", y = "word", fill_by = "group")

# Faceting
SplitBarPlot(data, x = "count", y = "word", facet_by = "group",
             fill_name = "Direction")

# Per-split palettes
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score",
             split_by = "group",
             palette = c(A = "Reds", B = "Blues", C = "Greens"))

# keep_na and keep_empty examples
data <- data.frame(
    word = factor(c("apple", "banana", "cherry", NA, "elderberry",
         "It is a very long term with a lot of words"),
         levels = c("apple", "banana", "cherry", "date", "elderberry",
             "unused", "It is a very long term with a lot of words")),
    count = c(-10, 20, NA, 40, 10, 34),
    score = c(1, 2, 3, 4, 5, 3.2),
    group = factor(sample(c("A", "A", "B", "B", "C", "C")),
         levels = c("A", "B", "C", "D"))
)

# Default: NA and empty levels dropped
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score")

# Keep NA and empty levels
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score",
             keep_na = TRUE, keep_empty = TRUE)

# Keep with faceting
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score",
             keep_na = TRUE, keep_empty = TRUE, facet_by = "group")

# Keep NA, hide empty levels (reserve colours)
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score",
             keep_na = TRUE, keep_empty = "level")

# Per-column control
SplitBarPlot(data, x = "count", y = "word", alpha_by = "score",
             keep_na = list(word = FALSE), keep_empty = list(word = TRUE))

# Control fill colour scale limits
SplitBarPlot(data, x = "count", y = "word", fill_by = "score",
             lower_cutoff = 1, upper_cutoff = 4)

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