stat_last_value: Add labels or points to the last value of a line chart

In ggsurveillance: Tools for Outbreak Investigation/Infectious Disease Surveillance

Add labels or points to the last value of a line chart

Description

Creates a label, point or any geom at the last point of a line (highest x value). This is useful for line charts where you want to identify each line at its endpoint, write the last value of a time series at the endpoint or just add a point at the end of a geom_line. This functions also nudges the last value relative to the length of the x-axis. The function automatically positions the label slightly to the right of the last point. There are 5 functions:

• stat_last_value(): The core statistical transformation that identifies the last point of a line (e.g. last date of the time series).

• geom_label_last_value(): Adds the last y value or a custom label after the last observation using geom_label.

• geom_text_last_value(): Adds the last y value or a custom text after the last observation using geom_text.

• geom_label_last_value_repel(): Adds non-overlapping labels with geom_label_repel.

• geom_text_last_value_repel(): Adds non-overlapping text with geom_text_repel.

Usage

stat_last_value(
  mapping = NULL,
  data = NULL,
  geom = "point",
  position = "identity",
  nudge_rel = 0,
  nudge_add = 0,
  expand_rel = 0,
  expand_add = 0,
  labeller = NULL,
  ...,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

geom_label_last_value(
  mapping = NULL,
  data = NULL,
  stat = "last_value",
  position = "identity",
  nudge_rel = 0.015,
  nudge_add = 0,
  expand_rel = 0.05,
  expand_add = 0,
  labeller = NULL,
  hjust = 0,
  ...,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

geom_text_last_value(
  mapping = NULL,
  data = NULL,
  stat = "last_value",
  position = "identity",
  nudge_rel = 0.015,
  nudge_add = 0,
  expand_rel = 0.035,
  expand_add = 0,
  labeller = NULL,
  hjust = 0,
  ...,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

geom_label_last_value_repel(
  mapping = NULL,
  data = NULL,
  stat = "last_value_repel",
  position = "identity",
  nudge_rel = 0.03,
  nudge_add = 0,
  expand_rel = 0.05,
  expand_add = 0,
  labeller = NULL,
  hjust = 0,
  direction = "y",
  min.segment.length = 0.5,
  ...,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

geom_text_last_value_repel(
  mapping = NULL,
  data = NULL,
  stat = "last_value_repel",
  position = "identity",
  nudge_rel = 0.015,
  nudge_add = 0,
  expand_rel = 0.035,
  expand_add = 0,
  labeller = NULL,
  hjust = 0,
  direction = "y",
  min.segment.length = 0.5,
  ...,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

Arguments

mapping	Set of aesthetic mappings created by aes. Commonly used mappings: x: position on x-axis y: position on y-axis label: text to display (defaults to the last y value)
data	The data frame containing the variables for the plot
geom	The geometric object to use to display the data for this layer. When using a ⁠stat_*()⁠ function to construct a layer, the geom argument can be used to override the default coupling between stats and geoms.
position	Position adjustment. Defaults to "identity"
nudge_rel	Numeric value specifying how far to nudge the label to the right, relative to the range of the x-values of the data. Defaults to 0.015 (1.5% of axis width) for labels.
nudge_add	Numeric value specifying an absolute amount to nudge the label (in units of the x-axis).
expand_rel	Numeric value specifying how far to expand the axis limits, relative to the range of the x-values of the data. This can be used to create room for longer text/labels. For repel functions this has to be large enough to place the text to achieve good results.
expand_add	Numeric value specifying an absolute amount to expand the axis limits (in units of the x-axis).
labeller	Label function to format the last value. E.g. scales::label_percent(), scales::label_number(), scales::label_dictionary().
...	Other arguments passed to geom_label, geom_text, geom_label_repel or geom_text_repel.
na.rm	If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.
show.legend	logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.
inherit.aes	If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().
stat	The statistical transformation to use on the data. Defaults to "last_value"
hjust	Horizontal text alignment. Defaults to left aligned (0).
direction	Direction in which to repel the labels. See geom_text_repel.
min.segment.length	Minimum length of the leader line segments. See geom_text_repel.

Details

The following calculated stats can be used further in aes:

• after_stat(x0): the highest x value

• after_stat(y): the y value of the observation with the highest x value.

• after_stat(label_formatted): the formatted y value using the labbeller.

Value

A ggplot2 layer that can be added to a plot

Examples

# Basic example with last value labels
library(ggplot2)

ggplot(economics, aes(x = date, y = unemploy)) +
  geom_line() +
  geom_text_last_value()

# Percentages
ggplot(economics, aes(x = date, y = unemploy / pop)) +
  geom_line() +
  geom_label_last_value(labeller = scales::label_percent(accuracy = 0.1))

# Multiple lines with custom labels
ggplot(economics_long, aes(x = date, y = value, color = variable)) +
  geom_line() +
  stat_last_value() + # Add a point at the end
  geom_label_last_value_repel(aes(label = variable),
    expand_rel = 0.1, nudge_rel = 0.05
  ) +
  scale_y_log10() +
  theme_mod_disable_legend()

ggsurveillance documentation built on June 8, 2025, 10:38 a.m.