highlight_color_by()

highlight_color_by.R

# The reprex
library(ggplot2)
data <- tibble::tribble(
  ~x,  ~group,        ~y, ~measure,  ~base,
  "FY18",   "aaa", 0.5603448,      260,    464,
  "FY15",   "aaa", 0.5081269,     1313,   2584,
  "FY19",   "aaa", 0.5799373,      185,    319,
  "FY16",   "aaa", 0.5225225,      580,   1110,
  "FY13",   "aaa", 0.4779116,      595,   1245,
  "FY17",   "aaa", 0.5502471,      334,    607,
  "FY14",   "aaa", 0.5339007,     1882,   3525,
  "FY20",   "aaa", 0.4960998,      318,    641,
  "FY21",   "aaa", 0.4765840,      173,    363,
  "FY21",   "bbb", 0.5135802,      208,    405,
  "FY20",   "bbb", 0.5384615,      259,    481,
  "FY17",   "bbb", 0.4628099,       56,    121,
  "FY18",   "bbb", 0.5474453,       75,    137,
  "FY15",   "bbb", 0.4705882,       72,    153,
  "FY19",   "bbb", 0.6083916,       87,    143,
  "FY14",   "bbb", 0.5097087,      105,    206,
  "FY16",   "bbb", 0.5395683,       75,    139,
  "FY13",   "bbb", 0.5432099,      132,    243,
  "FY14",   "ccc", 0.5326591,     2528,   4746,
  "FY21",   "ccc", 0.4320038,      899,   2081,
  "FY13",   "ccc", 0.5420887,     3265,   6023,
  "FY16",   "ccc", 0.5075188,      810,   1596,
  "FY15",   "ccc", 0.5116469,     1252,   2447,
  "FY18",   "ccc", 0.4206349,      477,   1134,
  "FY17",   "ccc", 0.4564565,      456,    999,
  "FY19",   "ccc", 0.4651429,      407,    875,
  "FY20",   "ccc", 0.4759398,      633,   1330
)

highlight_color_by <- function(expr, hl_colour = "#018d47") {
  aes(color = I(ifelse({{ expr }}, !!hl_colour, "#AA43FA")))
}

ggplot(data, aes(x, y)) +
  geom_line(
    aes(group = group, !!!highlight_color_by(group == "ccc"))
  )


# Another example
set.seed(1)

data2 <- expand.grid(x = 1:10, group_A = gl(3, 1), group_B = gl(2, 1)) |>
  transform(y = rnorm(60))

ggplot(data2, aes(x, y)) +
  geom_line(
    aes(group = interaction(group_A, group_B),
        !!!highlight_color_by(group_B == 1))
  )
  
# Not just line geom - works with any geom that takes understands group & color
ggplot(data2, aes(sample(x), y)) +
  geom_path(aes(!!!highlight_color_by(group_B == 1 & group_A == 2))) +
  facet_grid(group_A ~ group_B)