Simulate the Birthday Problem

birthday_problem.R

# Ref: https://en.wikipedia.org/wiki/Birthday_problem
# Ref: https://www.scientificamerican.com/article/bring-science-home-probability-birthday-paradox/
library(magrittr)
library(dplyr)
people <- 23
simulations <- 1e5
expand.grid(id = 1:people,
            sim = 1:simulations) %>%
  mutate(bday = sample(365, simulations * people, replace = TRUE)) %>%
  group_by(sim) %>%
  summarize(anyDupes = anyDuplicated(bday) > 1) %>%
  group_by(anyDupes) %>%
  summarize(freq = n()) %>%
  mutate(pct = freq / sum(freq))