The game of life written in R with spdep

game-of-life-spdep.R

library(spdep)

n <- 25
geo <- sf::st_make_grid(
  cellsize = c(1, 1),
  offset = c(0, 0),
  n = n
) 

# create contiguity neighbors for the grid 
nb <- poly2nb(geo)

# create binary spatial weights matrix
listw <- nb2listw(nb, style = "B")

# initialize game of life
x <- sample(c(0, 1), n^2, prob = c(0.8, 0.2), replace = TRUE)

# this function plays one round and updates x globally 
play_round <- function(x, listw) {
  results <- lag.listw(listw, x)
  
  # 1. Any live cell with fewer than two live neighbours **dies**, as if by underpopulation.
  dead_by_underpop <- x == 1 & results < 2
  
  # 2. Any live cell with two or three live neighbours **lives** on to the next generation.
  alive_to_alive <- x == 1 & (results == 2 | results == 3)
  
  # 3. Any live cell with more than three live neighbours dies, as if by overpopulation.
  dead_by_overpop <- x == 1 &  results > 3
  
  # 4. Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.
  dead_to_alive <- x == 0 & results == 3
  
  alive <- alive_to_alive | dead_to_alive
  dead <- dead_by_overpop | dead_by_underpop
  
  # Update the state
  x[alive] <<- 1  
  x[dead] <<- 0  
}


for (i in seq_len(10)) {
  cat("playing round ", i, "\n")
  play_round(x, listw)
  print(plot(sf::st_sf(x = x, geo)))
  Sys.sleep(0.5)
}