expansion.R

library(tidyverse)
library(gganimate)
library(sf)
CLUSTERS <- 100
map(0:50,function(max.iter){
  set.seed(12)
  df <- data.frame(x = runif(100000,0,1000),
                   y = runif(100000,0,1000))
  centers <- data.frame(x = 500 + runif(CLUSTERS,-100,100),
                        y = 500 + runif(CLUSTERS,-100,100))
  if(max.iter > 0){
    out <- kmeans(df,centers,iter.max = max.iter,algorithm = "Forgy")$centers %>% as.data.frame()  
  }else{
    out <- centers
  }
  out$iter <- max.iter
  out$point <- 1:CLUSTERS
  out1 <- out %>% 
    st_as_sf(coords=c("x","y"))
  env1 <- st_polygon(list(matrix(c(0,0,1000,0,1000,1000,0,1000,0,0),ncol=2, byrow=TRUE))) %>% st_sfc()
  out2 <- out1 %>%  
    summarise() %>% 
    st_voronoi(env1) %>% 
    st_collection_extract() %>% 
    st_join(out1) %>% 
    st_intersection(env1) %>% 
    mutate(area = st_area(geometry)) 
  out2
}) %>% 
  bind_rows() %>% 
  ggplot(aes(group = point,fill = log(area))) + 
  geom_sf() + 
  transition_states(iter) + 
  coord_sf(xlim = c(0,1000),ylim = c(0,1000)) + 
  scale_fill_viridis_c()