Likelihood and coin-flips (Combinatorics and Likelihood Connection using #rstats)

binomialCoins

### Likelihood of getting 3 heads out of 8 flips given a fair coin
n = 8
k = 3
steps = 10001 # Non zero ending to get likelihood; best if > 10000
p_grid = seq(0,1,length.out = steps)
prior = rep(1, steps)
likelihood = dbinom(k, n, prob = p_grid)
  # unstd.posterior = likelihood*prior
  # posterior = unstd.posterior/sum(unstd.posterior)
  # plot(p_grid, posterior)

plot(p_grid, likelihood)
abline(v = .5, col = "red")

gridFind = cbind(p_grid, likelihood)
findProb = .5
gridFind[which(abs(p_grid - findProb) == min(abs(p_grid - findProb))),]
# .2187 likelihood

# Combinations of 3 heads in 8 flips out of 2^n flips
(factorial(n)/(factorial(k)*factorial(n - k))) / ( 2 ^ n )
# 0.21875 likelihood