r_monte_carlo_anim.R

library(tidyverse)
library(gganimate)

set.seed(777)

points <- 2* 1e3

x <- runif(points, min = -1, max=1)
y <- runif(points, min=-1, max=1)
inside <- x^2 + y^2 < 1

df <- tibble(x, y, inside, frame=1:points)

ns <- map(1:points, ~(1:points)[1:.x])

estimates <-
  map_dbl(ns, ~df[.x,]$inside %>% mean %>% magrittr::multiply_by(4))

df$estimate <- estimates

estimates <- sprintf("%.8f", estimates)

n <- 1:points
df$pi_estimate <- as_factor(glue::glue("Estimate with {n} points = {estimates}"))

anim <- 
df %>%
  ggplot() +
  aes(x=x, y=y, color=inside) +
  geom_point() +
  coord_equal(xlim = c(-1,1), ylim=c(-1,1)) +
  theme_minimal() +
  theme(legend.position = "none") +
  labs(title="{current_frame}") +
  transition_manual(frame = pi_estimate, cumulative=TRUE)

anim2 <- 
df %>%
  ggplot() +
  aes(x=frame, y=estimate) +
  geom_point(size=0.2) +
  geom_hline(mapping=aes(yintercept=pi), linetype=2) +
  theme_minimal() +
  coord_cartesian(ylim=c(2.5,4.25)) +
  labs(x="Number of points", y="Estimated value") +
  transition_manual(frame=frame, cumulative=TRUE)

gif <- animate(anim,
               duration=10,
               fps = 60,
               height = 6,
               width = 6,
               units = "in",
               res = 300,
               renderer = ffmpeg_renderer())

# Save to mp4
anim_save(animation = gif, filename = "monte_carlo_circle.mp4")

gif <- animate(anim2,
               duration=10,
               fps = 60,
               height = 6,
               width = 6,
               units = "in",
               res = 300,
               renderer = ffmpeg_renderer())

# Save to mp4
anim_save(animation = gif, filename = "monte_carlo_circle_lineplot.mp4")