Why is my Martingale Simulation Function Failing to Work? - r

Question

I've just started getting back into coding, and I'm trying to write a few different functions to simulate betting strategies. The first I'm trying to simulate is the martingale strategy, a strategy where you place a roulette bet that has ~ 50% odds (black/red or even/odd) and each time you lose the bet, you double the bet until you won (or pass the max wager).
This is my current function which does not appear to be working. I'm not sure if the logic is sound (too many nested loops become confusing quickly). If anyone could point me in the right direction, that would be awesome.
possible_nums <- floor(runif(5, min=0, max=35)) # generate sequence of random numbers
wager = 5
tot_money <- 10000
wins <- 0
simulations <- 1:500
Martingale <- function(wager, tot_money) {
for(i in simulations) {
while(tot_money >= 5 & wager <= 500 ) { # stop betting if lose by running out of money or surpassing max wager
roll <- sample(possible_nums, 1) # roll number 1-35
if (roll %% 2 == 0) { # we will be betting even/odd (as opposed to black/red) for simulation
wins = wins + 1 # if even, we win
tot_money = tot_money + 5 # add 5 dollars to total money/balance if win
} else {
wager*2 # if roll was odd, double wager
}
}
}
}
print(wins)
print(tot_money)
}
Martingale(5, 1000) # run function
The function isn't even giving me an output when I run it. R seems very picky with the spacing of the brackets. I tried correcting them to not avail. If I get the function working, then I can correct the logic.
Thanks for any help!

Answer 1

You have one closing bracket too much, which closes the function before you print the results:
Martingale <- function(wager, tot_money) {
for(i in simulations) {
while(tot_money >= 5 & wager <= 500 ) { # stop betting if lose by running out of money or surpassing max wager
roll <- sample(possible_nums, 1) # roll number 1-35
if (roll %% 2 == 0) { # we will be betting even/odd (as opposed to black/red) for simulation
wins = wins + 1 # if even, we win
tot_money = tot_money + 5 # add 5 dollars to total money/balance if win
} else {
wager*2 # if roll was odd, double wager
}
}
}
} # <-- this one is too much,
print(wins)
print(tot_money)
}
Also note that your code will NOT terminate: you only increase tot_money, and do not modify the value of wager.
Let me note that you do not simulate a 50% chance: you choose at the beginning 5 random integers below 35 and take samples from those; if you want to simulate an odd/even change, you are better off with rbinom(1, 1, .5).
You might want to swap the way this is simulated and run the simulation-loop outside the Martingale function, and return the values and store them in a array:
Martingale2 <- function(wager, tot_money) {
while(tot_money >= 5 & wager <= 500 ) {
roll <- rbinom(1, 1, .5)
if (roll == 0) {
wins <- wins + 1
tot_money <- tot_money + 5
} else {
tot_money <- tot_money - wager
wager <- wager*2
}
}
list(wins = wins, tot_money = tot_money)
}
simulations <- 500
simulation_results <- t(replicate(simulations, Martingale2(5, 1000)))