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Label the outliers

Source: R/marks.R
mark_outlier_label.Rd

mark_outlier_label() labels only the outlying points — the extremes, where the story usually is — instead of every datum. It keeps the rows whose y is an outlier (per colour/fill group) and labels just those, repelled apart with the same solver as mark_text(). Layer it over the raw points.

Usage

mark_outlier_label(
  plot,
  ...,
  method = c("iqr", "sd"),
  k = 1.5,
  size = NULL,
  repel = TRUE,
  box_padding = 1,
  min_segment_length = 2,
  blend = NULL,
  data = NULL
)

Arguments

plot

A PlotSpec (from vplot()).

...

Encodings (tidy-eval): x, y, an optional label (what to write on each outlier), and optionally color / fill to detect outliers within each group.

method

Outlier rule: "iqr" (Tukey's, the default) or "sd".

k

Threshold multiplier — IQR whisker length (default 1.5) or number of standard deviations.

size

Font size in points.

repel

Move overlapping labels apart (force-directed, ggrepel-style), with leader lines to the points? Single cartesian panel only.

box_padding

Extra space (mm) kept around each label box during repulsion.

min_segment_length

Shortest leader line (mm) worth drawing; a label that barely moved gets none.

blend

Optional blend mode for compositing this layer against what is already drawn beneath it (the panel and earlier layers), one of the CSS mix-blend-mode names, e.g. "multiply", "screen", "darken". The whole layer composites as one isolated group (not per element).

data

Optional layer data frame; overrides the plot data for this layer.

Value

The modified PlotSpec.

Details

The default method = "iqr" flags y outside [Q1 - k*IQR, Q3 + k*IQR] (the boxplot whisker rule); method = "sd" flags |y - mean| > k * sd. Map a label to name each outlier; with none mapped, the outlier's y value is the label.

See also

mark_text(), mark_boxplot()

Examples

vplot(mtcars) |>
  mark_point(x = wt, y = mpg) |>
  mark_outlier_label(x = wt, y = mpg, label = rownames(mtcars))