Multi-series line plot (internal) — LinePlotGrouped • plotthis

Core implementation for drawing a multi-series line plot. This is the workhorse behind LinePlotAtomic for grouped data – it takes a single data frame with a group_by column and returns a ggplot object. Each group receives its own line rendered in a distinct colour from the palette, with optional error bars, highlighted points, per-group horizontal reference lines, and background stripes.

Usage

LinePlotGrouped(
  data,
  x,
  y = NULL,
  group_by,
  group_by_sep = "_",
  facet_by = NULL,
  add_bg = FALSE,
  bg_palette = "stripe",
  bg_palcolor = NULL,
  bg_alpha = 0.2,
  add_errorbars = FALSE,
  errorbar_width = 0.1,
  errorbar_alpha = 1,
  errorbar_color = "grey30",
  errorbar_linewidth = 0.75,
  errorbar_min = NULL,
  errorbar_max = NULL,
  errorbar_sd = NULL,
  highlight = NULL,
  highlight_size = pt_size - 0.75,
  highlight_color = "red2",
  highlight_alpha = 0.8,
  pt_alpha = 1,
  pt_size = 5,
  add_hline = FALSE,
  hline_type = "solid",
  hline_width = 0.5,
  hline_color = "black",
  hline_alpha = 1,
  line_type = "solid",
  line_width = 1,
  line_alpha = 0.8,
  theme = "theme_this",
  theme_args = list(),
  palette = "Paired",
  palcolor = NULL,
  palreverse = FALSE,
  x_text_angle = 0,
  aspect.ratio = 1,
  legend.position = "right",
  legend.direction = "vertical",
  title = NULL,
  subtitle = NULL,
  xlab = NULL,
  ylab = NULL,
  keep_empty = FALSE,
  keep_na = FALSE,
  ...
)

Arguments

data

A data frame.

x

A character string specifying the column name of the data frame to plot for the x-axis.

y

A character string specifying the column name of the data frame to plot for the y-axis.

group_by

A character vector of column names to group the data by. Each unique combination becomes a separate line. Multiple columns are concatenated with group_by_sep. When NULL, the LinePlotSingle path is used instead.

group_by_sep

A character string used to join multiple group_by column values into a single group identifier. Default "_".

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

add_bg

A logical value. When TRUE, alternating background stripes are drawn via bg_layer(). Default FALSE.

bg_palette

A character string specifying the palette for the background stripe colours. Default "stripe".

bg_palcolor

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

bg_alpha

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

add_errorbars

A logical value. When TRUE, error bars are added via geom_errorbar(). Requires errorbar_sd or errorbar_min/errorbar_max. Default FALSE.

errorbar_width

A numeric value for the width of the error bar caps. Default 0.1.

errorbar_alpha

A numeric value in [0, 1] for the transparency of error bars. Default 1.

errorbar_color

A character string for the colour of the error bars. When "line", error bars are coloured the same as the lines (by x when color_line_by_x = TRUE, or single colour otherwise). Default "grey30".

errorbar_linewidth

A numeric value for the line width of error bars. Default 0.75.

errorbar_min

A character string naming the column with the lower error bar bound. Ignored when errorbar_sd is provided.

errorbar_max

A character string naming the column with the upper error bar bound. Ignored when errorbar_sd is provided.

errorbar_sd

A character string naming the column with the standard deviation. When errorbar_min and errorbar_max are not provided, error bars are computed as y +/- errorbar_sd.

highlight

A vector of row indices, row names, a single string expression (e.g. "y > 10") filtering rows to highlight, or TRUE to highlight all points. When NULL (default), no highlighting is applied.

highlight_size

A numeric value for the size of highlighted points. Defaults to pt_size - 0.75.

highlight_color

A character string for the colour of highlighted points. Default "red2".

highlight_alpha

A numeric value in [0, 1] for the transparency of highlighted points. Default 0.8.

pt_alpha

A numeric value in [0, 1] for the transparency of points. Default 1.

pt_size

A numeric value for the point size. Default 5.

add_hline

A numeric value specifying the y-intercept of a horizontal reference line. When FALSE (default), no line is drawn.

hline_type

A character string specifying the line type of the horizontal reference line. Default "solid".

hline_width

A numeric value for the width of the horizontal reference line. Default 0.5.

hline_color

A character string for the colour of the horizontal reference line. Default "black".

hline_alpha

A numeric value in [0, 1] for the transparency of the horizontal reference line. Default 1.

line_type

A character string specifying the line type. Default "solid".

line_width

A numeric value for the line width (in mm). Default 1.

line_alpha

A numeric value in [0, 1] for the transparency of the line. Default 0.8.

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.

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_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.

...

Additional arguments.

Value

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

Architecture

ggplot dispatch – selects gglogger::ggplot or ggplot2::ggplot based on getOption("plotthis.gglogger.enabled").
Column resolution – x (forced to factor), y, group_by (multi-column concatenation supported), and facet_by are validated via check_columns.
Count aggregation – when y = NULL, the count of observations per (x, group_by, facet_by) combination is computed and used as y.
Error bar validation – if add_errorbars = TRUE, checks that either errorbar_min/errorbar_max or errorbar_sd is provided.
NA / empty-level handling – process_keep_na_empty() applies keep_na and keep_empty policies.
Highlight parsing – highlight (indices, row names, expression string, or TRUE) is resolved to a subset of data rows.
Background layer – when add_bg = TRUE, alternating background stripes are drawn via bg_layer().
Colour assignment – palette_this() assigns colours to all group_by levels (including NA, defaulting to "grey80").
Horizontal reference line – when add_hline is set, one or more geom_hline() are added. If hline_color = TRUE, each horizontal line is coloured to match the corresponding group colour, and add_hline can be a named vector/ list mapping groups to intercept values.
Line rendering – lines are coloured and grouped by group_by via geom_line() with aes(color = group_by, group = group_by) and scale_color_manual().
Error bars – when add_errorbars = TRUE, three colour modes are supported: follow the line colour ("line"), track group_by colours, or use a constant colour. Error bars are added via geom_errorbar().
Point rendering – points are filled per group via geom_point() with aes(fill = group_by) and scale_fill_manual().
Highlight overlay – an additional geom_point() layer draws highlighted rows in the specified colour and size.
Plot assembly – scale_x_discrete(), labs(), theme application, axis styling (angle, grid lines), and legend positioning.
Dimension calculation – calculate_plot_dimensions() computes height and width attributes (in inches) from x-axis category count, aspect ratio, and legend metrics (legend entries reflect group levels rather than x levels).