Aesthetics in R

Color, shape and size can carry data, or be fixed constants.

library(ggplot2)
library(tibble)

runs <- tibble(
  day = rep(1:3, 2),
  tpm = c(88, 92, 96, 99, 104, 101),
  lang = rep(c("r", "python"), each = 3),
  errors = c(3, 2, 1, 0, 1, 2)
)

mapped <- ggplot(runs, aes(day, tpm, colour = lang, size = errors)) +
  geom_point()

fixed <- ggplot(runs, aes(day, tpm, group = lang)) +
  geom_line(colour = "steelblue", linewidth = 1)

print(names(mapped$mapping))
print(length(fixed$layers))
ggsave(tempfile(fileext = ".png"), mapped, width = 4, height = 3, dpi = 100)

How it works

1. Inside aes a value maps a column; outside it sets a constant.
2. That distinction is the most common ggplot mistake.
3. group controls which rows join up.

Keywords and builtins used here

• aes
• c
• geom_line
• geom_point
• ggplot
• ggsave
• length
• library
• names
• print
• rep
• tempfile
• tibble

The run, in numbers

Lines

19

Characters to type

494

Tokens

171

Three-star pace

95 tpm

At the three-star pace of 95 tokens a minute, this run takes about 108 seconds.

Type this snippet

Step 2 of 3 in The grammar, step 2 of 15 in ggplot2.

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