Game of Life in R

life.r

shiftMatrix <- function(mx, dr, dc) {
	#Shift the matrix by dr (delta r) rows and dc columns
	#by adding e.g. dr rows of zeros and removing dr rows from the other side 
	
	nr <- nrow(mx)
	nc <- ncol(mx)
	
	#If the matrix is shifted by more than its nrow or ncol, we get a matrix of zeros 
	if (abs(dr) >= nr || abs(dc) >= nc) {
		mx <- matrix(0, nrow = nr, ncol = nc)
		return(mx)
	}
	
	#Rows:
	if (dr > 0) {
		mx <- rbind(mat.or.vec(dr, nc), mx)
		mx <- mx[1:nr,]
	} else if (dr < 0) {
		mx <- rbind(mx, mat.or.vec(-dr, nc))
		mx <- mx[(1 - dr):(nr - dr),]
	}
	
	#Columns:
	if (dc > 0) {
		mx <- cbind(mat.or.vec(nr, dc), mx)
		mx <- mx[,1:nc]
	} else if (dc < 0) {
		mx <- cbind(mx, mat.or.vec(nr, -dc))
		mx <- mx[,(1 - dc):(nc - dc)]
	}
	return(mx)
}

life_cycle <- function(mx) {
	#Move the board one generation forward
	
	mx0 <- matrix(0, nrow = nrow(mx), ncol = ncol(mx))
	
	#Produce 8 "shifted" boards and add them up
	for (n in (-1:1)) {
		for (m in (-1:1)) {
			if (n !=0 || m !=0) {
				mx0 <- mx0 + shiftMatrix(mx, n, m)
			}
		}
	}
	
	#Deaths and births
	mx[mx0 > 3 | mx0 < 2] <- 0
	mx[mx0 == 3] <- 1
	return(mx)
}

#Initialization of parameters
n_rows <- 100
n_cols <- 100
n_cells <- n_rows * n_cols
n_cycles <- 100
sleep_time <- 0.1
clrs <- c("#f0f0f0", "#2f81c1") #colors for empty squares and cells
rnd_threshold <- 0.3 # 0 - empty board; 1 - all squares are filled
set.seed(1) #Random seed

#Create a board and plot it 
board <- matrix(0, nrow = n_rows, ncol = n_cols)
board[runif(n_cells, 0, 1) < rnd_threshold] <- 1
image(board, axes = FALSE, col = clrs)

#The main cycle
for (i in (1:n_cycles)) {
	Sys.sleep(sleep_time)
	board <- life_cycle(board)
	image(board, axes = FALSE, col = clrs)
}

Hi Vadim,
wow, totally different approach! I think yours scales better. I dig it,
had never seen the function 'mat.or.vec()' before
Tim