How to import printed tone audiograms in R and plot them with ggplot2

tone_audiogram.R

library(magrittr)

# Frequencies tested in tone audiograms
audiogram_frequencies <- c(0.125, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8)
# Simulate hearing loss data in wide format
sample_df <- data.frame(
  frequency = audiogram_frequencies,
  air_right = sample(40:70, size = 11),
  air_left = sample(50:90, size = 11),
  bone_right = sample(0:30, size = 11),
  bone_left = sample(0:30, size = 11)
) %>%
  # Transform into tidy data (long) format
  # The original data set stores information about conduction and side in
  # variable names,, but we want this information to be encoded in factors.
  # In fact, there is just one measurement, the hearing loss,
  # which depends on the frequency, conduction, and side factors.
  tidyr::pivot_longer(
    cols = air_right:bone_left,
    names_to = c("conduction", "side"),
    names_sep = "_",
    names_transform = list(
      conduction = ~ factor(.x, levels = c("air", "bone")),
      side = ~ factor(.x, levels = c("right", "left"))
    ),
    values_to = "hl"
  ) %>%
  # Drop rows with missing values
  tidyr::drop_na(hl) %>%
  # Plot data as audiogram
  ggplot2::ggplot(
    ggplot2::aes(
      x = .data$frequency, y = .data$hl,
      group = .data$conduction, color = .data$side
    )
  ) +
  ggplot2::geom_point(
    ggplot2::aes(shape = forcats::fct_cross(.data$conduction, .data$side)),
    size = 4
  ) +
  ggplot2::geom_line(ggplot2::aes(linetype = .data$conduction)) +
  ggplot2::scale_x_continuous(
    breaks = audiogram_frequencies,
    labels = paste(audiogram_frequencies),
    minor_breaks = NULL,
    trans = "log"
  ) +
  ggplot2::scale_y_reverse(
    breaks = seq(-10, 100, 10),
    minor_breaks = NULL
  ) +
  ggplot2::scale_shape_manual(
    values = c(">", "o", "<", "x"),
    breaks = c("bone:right", "air:right", "bone:left", "air:left")
  ) +
  ggplot2::expand_limits(y = c(-10, 100)) +
  ggplot2::facet_wrap(ggplot2::vars(.data$side)) +
  ggplot2::labs(
    x = "Frequency in kHz",
    y = "Hearing loss in dB (HL)",
    shape = "side X conduction"
  ) +
  ggplot2::theme_bw()
ggplot2::ggsave("audiogram.pdf")