Use R to locate the coordinates of places of interest on a map of Kanto

kanto-points-lines.R

# See blogpost about this
#   https://www.rostrum.blog/2021/11/04/kanto-locator/

# Function: download and plot a PNG file

plot_map <- function(png_path) {
  
  tmp <- tempfile()
  download.file(png_path, tmp, quiet = TRUE)
  img <- png::readPNG(tmp)
  par(mar = rep(0, 4))
  plot.new()
  grid::grid.raster(img, x = 0.5, y = 0.5)
  
}

kanto_path <- 
  "https://cdn2.bulbagarden.net/upload/8/86/Kanto_Town_Map_RBY.png"

plot_map(kanto_path)  # plot town map of Kanto

# Function: prompt user to click for list of points on plot

locate_points <- function(places) {
  
  places_list <- vector("list", length(places)) |> setNames(places)
  
  for (i in places) {
    cat(paste0("Click on ", i, "... "))
    places_list[[i]] <- locator(1, type = "p")
    cat("found.\n")
  }
  
  places_df <- do.call(rbind, places_list) |> data.frame()
  
}

kanto_names <- c(
  "Pallet Town", "Viridian City", "Viridian Forest", "Pewter City", 
  "Mt Moon", "Cerulean City", "Rock Tunnel", "Vermilion City", 
  "Lavender Town", "Celadon City", "Fuchsia City", "Saffron City", 
  "Seafoam Islands", "Cinnabar Island", "Victory Road",
  "Indigo Plateau"
)

kanto_pts <- locate_points(kanto_names)  # interactive plot clicking

# Plot: cities are large red points, other places are small blue
# points; labels larger for cities; lines connect the cities
# in the order of playthrough.

kanto_pts$city <- ifelse(
  grepl("Town|City|Island$", rownames(kanto_pts)), 
  TRUE, FALSE
)

par(mar = rep(0, 4))

plot(kanto_pts$x, kanto_pts$y, axes = FALSE)

lines(kanto_pts$x, kanto_pts$y, col = "grey95", lwd = 5)

points(
  kanto_pts$x, kanto_pts$y,
  pch = 16,
  cex = ifelse(kanto_pts$city, 2, 1),
  col = ifelse(kanto_pts$city, "red", "blue")
)

text(
  kanto_pts$x, kanto_pts$y,
  gsub(" ", "\n", row.names(kanto_pts)),
  cex = ifelse(kanto_pts$city, 0.7, 0.4),
  pos = c(1, 1, 1, 4, 1, 1, 2, 1, 2, 1, 1, 1, 3, 3, 1, 1),
  family = "Press Start 2P"  # from Google Fonts
)

# Plot: each point is a city coloured with its name
# e.g. Fuchsia City is pink

kanto_cities <- 
  kanto_pts[kanto_pts$city | rownames(kanto_pts) == "Indigo Plateau", ]

kanto_cities$colour <- c(  # close-enough named R colours
  "white", "aquamarine4", "grey57", "royalblue3 ",
  "red3 ", "lavender", "darkseagreen2", "magenta",
  "tomato2", "orangered2", "blue"
) 
par(mar = rep(0, 4))
with(kanto_cities, plot(x, y, axes = FALSE))
with(kanto_cities, points(x, y, pch = 22, cex = 4, bg = colour))