Error bar / interval layer — mark

Adds interval bars showing pre-computed intervals (stat = "identity", the default: ymin/ymax come straight from the data) or statistical entities computed per group (stat = "mean_sem", "mean_sd", "mean_range", "mean_ci95"): the interval is aggregated from the raw y values of each x group with no manual pre-computation.

Usage

mark_errorbar(
  plot,
  mapping = NULL,
  data = NULL,
  position = NULL,
  ...,
  stat = "identity",
  level = 0.95,
  ci_method = c("normal", "boot"),
  seed = NULL,
  width = 0.5,
  orientation = c("vertical", "horizontal"),
  caps = TRUE,
  rasterize = FALSE,
  rasterize_dpi = 300,
  rasterize_dev = "cairo"
)

Arguments

plot: A plotit object
mapping: Optional new aesthetics. With stat = "identity" it must include the interval columns for the chosen orientation (ymin/ymax vertical, xmin/xmax horizontal); with a statistical entity it only needs x (group) and y (value).
data: Optional data for this layer
position: Position adjustment.
...: Other arguments passed to the underlying geom
stat: Statistical entity: "identity" (pre-computed intervals, no implicit aggregation) or one of "mean_sem", "mean_sd", "mean_range", "mean_ci95" (per-group aggregation of y).
level: Confidence level for stat = "mean_ci95", in (0, 1) (default 0.95).
ci_method: "normal" (default, t-based normal approximation) or "boot" (percentile bootstrap of the mean; requires seed).
seed: RNG seed for ci_method = "boot"; required for reproducibility of the bootstrap.
width: Size of the error bar caps as a fraction of the resolution of the data. When NULL (default) the style token width_errorbar (0.4) applies for caps = TRUE. Ignored when caps = FALSE.
orientation: "vertical" (default) or "horizontal".
caps: If TRUE (default), draw end caps; FALSE renders bare interval lines (geom_linerange).
rasterize: If TRUE, rasterize via ggrastr::rasterise().
rasterize_dpi: DPI for rasterization (default 300).
rasterize_dev: Graphics device for rasterization (default "cairo").

Value

Modified plotit object

Details

Vertical bars (default) map the position on x and the interval on ymin/ymax; horizontal bars map the position on y and the interval on xmin/xmax (G2's rangeX/rangeY semantics). Set caps = FALSE for plain interval lines without end caps (Vega-Lite's errorband).

References

Vega-Lite: Errorbar / Errorband (extent: stderr <-> sem, stdev <-> sd, ci <-> ci95)

AntV G2: Range

Examples

df <- data.frame(
  x = c("A", "B"), y = c(10, 20), ymin = c(8, 18), ymax = c(12, 22)
)
plotit(df, encode(x = x, y = y, ymin = ymin, ymax = ymax)) |>
  mark_errorbar(width = 0.3)


# statistical entity: mean +- sem aggregated per group from raw y
plotit(iris, encode(x = Species, y = Sepal.Length)) |>
  mark_errorbar(stat = "mean_sem")


# horizontal interval (position on y, range on x)
dfh <- data.frame(
  y = c("A", "B"), x = c(10, 20), xmin = c(8, 18), xmax = c(12, 22)
)
plotit(dfh, encode(x = x, y = y, xmin = xmin, xmax = xmax)) |>
  mark_point() |>
  mark_errorbar(orientation = "horizontal", caps = FALSE)