Intervals: geom_linerange

Mix.install([
  {:giggly, path: Path.join(__DIR__, "..")},
  {:kino, "~> 0.19"}
  ])

About this notebook

This notebook follows the examples on ggplot2's reference page for geom_linerange(), which covers geom_crossbar(), geom_errorbar(), geom_errorbarh() and geom_pointrange() too, in the order the page gives them. Each example shows ggplot2's code first and then Giggly's. An example Giggly cannot draw yet keeps its ggplot2 code and names what it is waiting for, so the page is also a list of what remains.

These geoms each draw an interval: a range from ymin to ymax at an x, or from xmin to xmax at a y when turned on its side. geom_linerange() draws it as a line, geom_pointrange() as a line with a point at y, geom_errorbar() as a line capped at each end, and geom_crossbar() as a box with a line across it at y. geom_errorbarh() is deprecated in favour of geom_errorbar(orientation = "y"). Giggly has none of them yet.

Lines, points, crossbars and error bars

# Create a simple example dataset
df <- data.frame(
  trt = factor(c(1, 1, 2, 2)),
  resp = c(1, 5, 3, 4),
  group = factor(c(1, 2, 1, 2)),
  upper = c(1.1, 5.3, 3.3, 4.2),
  lower = c(0.8, 4.6, 2.4, 3.6)
)

p <- ggplot(df, aes(trt, resp, colour = group))
p + geom_linerange(aes(ymin = lower, ymax = upper))
p + geom_pointrange(aes(ymin = lower, ymax = upper))
p + geom_crossbar(aes(ymin = lower, ymax = upper), width = 0.2)
p + geom_errorbar(aes(ymin = lower, ymax = upper), width = 0.2)

Not in Giggly yet: geom_linerange(), geom_pointrange(), geom_crossbar() and geom_errorbar() and their width option.

Horizontal intervals

# Flip the orientation by changing mapping
ggplot(df, aes(resp, trt, colour = group)) +
  geom_linerange(aes(xmin = lower, xmax = upper))

Mapping xmin and xmax rather than ymin and ymax turns the intervals on their side.

Not in Giggly yet: geom_linerange().

Lines through the group means

# Draw lines connecting group means
p +
  geom_line(aes(group = group)) +
  geom_errorbar(aes(ymin = lower, ymax = upper), width = 0.2)

Not in Giggly yet: geom_errorbar() and its width option.

Dodging bars and error bars

# If you want to dodge bars and errorbars, you need to manually
# specify the dodge width
p <- ggplot(df, aes(trt, resp, fill = group))
p +
 geom_col(position = "dodge") +
 geom_errorbar(aes(ymin = lower, ymax = upper), position = "dodge", width = 0.25)

Each layer is dodged by its own width here, so the narrower error bars do not line up with the bars.

Not in Giggly yet: geom_errorbar() and its width option. Giggly dodges columns already: Giggly.Plot.geom_col/3 with position: :dodge.

Dodging by one width

# Because the bars and errorbars have different widths
# we need to specify how wide the objects we are dodging are
dodge <- position_dodge(width=0.9)
p +
  geom_col(position = dodge) +
  geom_errorbar(aes(ymin = lower, ymax = upper), position = dodge, width = 0.25)

Not in Giggly yet: position_dodge()'s options, and geom_errorbar() and its width option. Giggly names a position by an atom, position: :dodge, which takes no options.

Dodging with padding

# When using geom_errorbar() with position_dodge2(), extra padding will be
# needed between the error bars to keep them aligned with the bars.
p +
geom_col(position = "dodge2") +
geom_errorbar(
  aes(ymin = lower, ymax = upper),
  position = position_dodge2(width = 0.5, padding = 0.5)
)

Not in Giggly yet: geom_errorbar(). Giggly.Plot.position_dodge2/1 takes padding: but no width:, and R ignores width = 0.5 here: the error bars have widths of their own, which position_dodge2() dodges by.