show_cutoffs: Add Cutoff Markers to a Distribution

In coursekata: Packages and Functions for 'CourseKata' Courses

Add Cutoff Markers to a Distribution

Description

Usage

show_cutoffs(
  object = NULL,
  part,
  color = "#1e3a8a",
  size = 4,
  show_labels = FALSE
)

Arguments

object	A ggplot of one distribution – a histogram, bar chart, density, dotplot, or gf_squareplot().
part	A distribution part, e.g. middle(Thumb, .95). Optional: without it, the part is read off the plot's fill aesthetic.
color	Marker/line color. Default "#1e3a8a".
size	Marker size. Default 4.
show_labels	Whether to annotate the cutoffs. Default FALSE.

Details

Adds empirical quantile cutoffs for a distribution part – middle(), tails(), upper(), lower(), or outer(). Short dashed stems end in downward triangles that touch the numeric axis. Optional callouts are drawn in the data panel. Repeated labelled calls are measured and placed together. Their boxes stay separate when the panel has room, and their routed leaders remain tied to the exact cutoffs.

In very small panels, leaders use a simple elbow connection if there is no room for an outward route. Labels keep their text and size, so they may overlap or be clipped. Enlarge the figure, use fewer facet columns, or set show_labels = FALSE when labels do not fit.

By default the part is read off the plot's fill aesthetic, e.g. fill = ~middle(Thumb, .95). Passing part overrides that reading: it marks whatever part is named there instead, and the fill (if any) is ignored – marking the 99% cutoffs on a plot shaded for the 95% is a deliberate, lossless override, not a mismatch.

show_cutoffs() refuses a plot whose first layer does not draw a distribution (a scatterplot, for instance) and, when part is given explicitly, a part that names a variable other than the one the plot puts on x.

Value

A ggplot object with cutoff markers and optional labels.

See Also

stat_cutoff() computes the same rule per panel; geom_cutoff() is the lower-level drawing component. guide_cutoff() can place cutoff anchors in a position guide instead.

Examples

gf_histogram(~Thumb, data = Fingers, binwidth = 5, fill = ~middle(Thumb, .95)) %>%
  show_cutoffs(show_labels = TRUE)

# an explicit part overrides the fill instead of requiring it to match
gf_histogram(~Thumb, data = Fingers, binwidth = 5, fill = ~middle(Thumb, .95)) %>%
  show_cutoffs(middle(Thumb, .99))

coursekata documentation built on Sept. 22, 2026, 1:08 a.m.