tidyverse-friendly (& hopefully more readable) version of the tweenr example

tidy-tweenr-example

library(tidyverse)
library(gganimate)
library(ggforce)
library(tweenr)

# Making up data
n_balls <- 20
d <- tibble(x = rnorm(n_balls),
            y = rnorm(n_balls),
            time = sample(100, n_balls),
            alpha = 0,
            size = 10,
            ease = "elastic-out",
            id = 1:n_balls) %>% 
  list()

d[[2]] <- d[[1]] %>% 
  mutate(time = time + 10,
         alpha = 1,
         size = 1,
         ease = "linear")

d[[3]] <- d[[2]] %>% 
  mutate(time = time + sample(50:100, n_balls),
         size = 3,
         ease = "bounce-out")

d[[4]] <- d[[3]] %>% 
  mutate(time = time + 10,
         y = min(y) - 0.5,
         size = 3,
         ease = "bounce-out")

d[[5]] <- d[[4]] %>% 
  mutate(time = max(time))

df <- reduce(d, bind_rows)

# Using tweenr
dt <- tween_elements(df, 'time', 'id', 'ease', nframes = 500)

# Animate with gganimate
p <- ggplot(data = dt) + 
  geom_point(aes(x=x, y=y, size=size, alpha=alpha, frame = .frame)) + 
  scale_size(range = c(0.1, 20), guide = 'none') + 
  scale_alpha(range = c(0, 1), guide = 'none') + 
  ggforce::theme_no_axes()

animation::ani.options(interval = 1/24)
gganimate(p, 'dropping balls.gif', title_frame = F)