Stuck in infinite loop, where is the problem I am seeing? - r

Question

My code is stuck in an infinite loop, with the stop sign occurring. I have read through it multiple times, can anyone help?
I am trying to run trials using samples of possession probabilities and the subsequent make probabilities for a basketball team. I am following along with a video and made sure each step was completed properly.
How can I tell where I am stuck in an infinite loop and how do I fix it?
mc_hoops_ex <- function(trials) {
prob_pos <- c(0.148, 0.544, 0.308, 0.256)
prob_2pm <- 0.524
prob_3pm <- 0.378
prob_ftm <- 0.761
prob_orb <- 0.319
a <- 1
pts_ct <- 0
while (a <= trials) {
pos_outcome <- sample(c(1:4), 1, prob = prob_pos)
if(pos_outcome == 2) {
pos_end <- 0
while (pos_end < 1) {
shot_prob <- runif(1)
if(shot_prob <= prob_2pm) {
pts_ct <- pts_ct + 2
pos_end <- 1
}
else {
orb_prob <- runif(1)
if(orb_prob >= prob_orb)
pos_end <- 1
}
}
}
}
if(pos_outcome == 3) {
pos_end <- 0
while (pos_end < 1) {
shot_prob <- runif(1)
if(shot_prob <= prob_3pm) {
pts_ct <- pts_ct + 3
pos_end <- 1
}
else {
orb_prob <- runif(1)
if(orb_prob >= prob_orb)
pos_end <- 1
}
}
}
if(pos_outcome == 4) {
pos_end <- 0
while (pos_end < 1) {
shot_prob <- runif(1)
if(shot_prob <= prob_ftm) {
pts_ct <- pts_ct + 1
pos_end <- 1
}
else {
orb_prob <- runif(1)
if(orb_prob >= prob_orb)
pos_end <- 1
}
}
}
a <- a + 1
print(pts_ct / trials)
print((pts_ct / trials) * 66.3)
}

Answer 1

This looks like R code, based on the syntax, <- assignment, and functions like c() and runif().
You have the following loop: while (a <= trials). This loop will continue running until the condition no longer holds. Since you initialize a <- 1, this loop will not stop unless (1) trials < 1, in which case the loop will not run a single time, or (2) a is incremented until a > trials.
We can see that the only time a is changed is near the bottom of the function: a <- a + 1. However, look closely at the braces. This increment is outside the while-loop, so it never occurs and the loop runs forever.
I'm not sure if this will produce the expected results, but a corrected version that does not have an infinite loop is given below.
mc_hoops_ex <- function(trials) {
prob_pos <- c(0.148, 0.544, 0.308, 0.256)
prob_2pm <- 0.524
prob_3pm <- 0.378
prob_ftm <- 0.761
prob_orb <- 0.319
a <- 1
pts_ct <- 0
while (a <= trials) {
pos_outcome <- sample(c(1:4), 1, prob = prob_pos)
if(pos_outcome == 2) {
pos_end <- 0
while (pos_end < 1) {
shot_prob <- runif(1)
if(shot_prob <= prob_2pm) {
pts_ct <- pts_ct + 2
pos_end <- 1
}
else {
orb_prob <- runif(1)
if(orb_prob >= prob_orb)
pos_end <- 1
}
}
}
# Removed the closing brace here
if(pos_outcome == 3) {
pos_end <- 0
while (pos_end < 1) {
shot_prob <- runif(1)
if(shot_prob <= prob_3pm) {
pts_ct <- pts_ct + 3
pos_end <- 1
}
else {
orb_prob <- runif(1)
if(orb_prob >= prob_orb)
pos_end <- 1
}
}
}
if(pos_outcome == 4) {
pos_end <- 0
while (pos_end < 1) {
shot_prob <- runif(1)
if(shot_prob <= prob_ftm) {
pts_ct <- pts_ct + 1
pos_end <- 1
}
else {
orb_prob <- runif(1)
if(orb_prob >= prob_orb)
pos_end <- 1
}
}
}
a <- a + 1
} # Added a closing brace here instead
print(pts_ct / trials)
print((pts_ct / trials) * 66.3)
}