Random Number Generator / Flip / A -B Generator - Run up to X in a string in R
I am trying to generate random results, for example from coin flip. I would like to run this A / B or head / tails generator until I get x of the same result sequentially.
I found this code online to transfer coins:
sample.space <- c(0,1)
theta <- 0.5 # this is a fair coin
N <- 20 # we want to flip a coin 20 times
flips <- sample(sample.space,
size=N,
replace=TRUE,
prob=c(theta,1-theta))
This works to generate 20 flips, but I want the "flip simulator" to run until I get x of the same result per line.
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3 answers
You can use a simple loop
n <- 10 # get this many 1s in a row
count <- runs <- 0 # keep track of current run, and how many total
while(runs < n) { # while current run is less than desired
count <- count+1 # increment count
runs <- ifelse(sample(0:1, 1), runs+1, 0) # do a flip, if 0 then reset runs, else increment runs
}
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One approach could be to generate a large number of coin flips and identify the first time you receive a specified number of consecutive flips using the function rle
:
first.consec <- function(num.consec, num.flip) {
flips <- sample(0:1, size=num.flip, replace=TRUE, prob=c(0.5, 0.5))
r <- rle(flips)
pos <- head(which(r$lengths >= num.consec), 1)
if (length(pos) == 0) NA # Did not get any runs of specified length
else sum(head(r$lengths, pos-1))
}
set.seed(144)
first.consec(10, 1e5)
# [1] 1209
first.consec(10, 1e5)
# [1] 2293
first.consec(10, 1e5)
# [1] 466
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Longer than @ nongkrong's answer, but you do get some output:
n <- 5
out <- 2
tmp2 <- 2
count <- 0
while (count < n-1) {
tmp <- sample(0:1,1)
out <- rbind(out, tmp)
ifelse(tmp == tmp2, count <- count+1, count <- 0)
tmp2 <- tmp
}
out <- data.frame(CoinFlip=out[-1])
out
Example:
> out
CoinFlip
1 1
2 0
3 1
4 0
5 0
6 0
7 0
8 0
0
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