library(data.table)
library(ggplot2)

DT <- `[`

jump_by <- function (x, by, start = 1, fill = NULL)  {
  if (!is.null(fill)) {
    x[-seq.int(start, length(x), by = by)] <- fill
  }
  else {
    x <- x[seq.int(start, length(x), by = by)]
  }
  return(x)
}



totals <- babynames::babynames |>
  as.data.table() |>
  DT(, .(total = sum(n)), by = .(year))


babynames::babynames |>
  as.data.table() |>
  DT(, ending := substr(name, nchar(name), nchar(name))) |>
  DT(ending %in% c("a", "e", "i", "o", "u", "y")) |>
  DT(, .(n = sum(n)), by = .(sex, year, ending)) |>
  DT(totals, on = c("year")) |>
  DT(, prop := n/total) |>
  ggplot(aes(year, prop)) +
  geom_line(data = \(x) x[, .(total = sum(prop)), by = .(ending, year)],
            aes(y = total), color = "gray40",
            size = 1) +
  geom_line(aes(color = sex), size = 1.5) +

  scale_color_manual("Sex", values = c("F" = "#F36F52",
                                       "M" = "#51C5DE"),
                     labels = c("F" = "Female",
                                "M" = "Male")) +
  scale_x_continuous(NULL, breaks = seq(1800, 2022, by = 10),
                     labels = \(x) jump_by(x, 2, fill = "")) +
  scale_y_continuous(NULL, labels = scales::percent_format()) +
  expand_limits(y = 0) +
  theme_minimal(base_size = 20) +
  theme(panel.grid.minor = element_blank(),
        axis.ticks.x = element_line(color = "gray40")) +
  labs(title = "US Babies Receiving Names Ending in... ") +
  facet_wrap(~paste0("-", ending), scale = "free", ncol = 2)