Reproduce color prime factorization chart

prime_factorization.R

#Reproduce this prime factorization poster in R
#https://twitter.com/stevenstrogatz/status/1295915404574040065?s=20

library(tidyverse)

#Prime factorization function from SO
# https://stackoverflow.com/questions/49974601/r-prime-factorization
get_prime_factors = function(x){
  n=c()
  i=2
  r=x
  while(prod(n)!=x){
    if(!r%%i) {n=c(n,i);r=r/i;i=1}
    i=i+1
  }
  n
}

get_prime_factors(9)

#Generate a color palette

#Control the first few primes...
# Make this similar to the original postcad
this_palette_start = tibble::tribble(
  ~r, ~g, ~b,
  255, 255, 255, #white = 1
    0, 102, 255, #blue = 2,
  255,   0, 51, #maroon = 3,
  255, 255,   0, #yellow = 5,
  102,  51, 153, #purple = 7,
  255,  51, 255, #pink = 11,
  204, 153, 102, #brown = 13,
  255, 102,   0 #orange = 17
  
)

#..., then add randoms for the rest
random_channels <- function(n, k=6){
  sample(seq(0, 255, length.out = k), n, replace = TRUE)
}

set.seed(43)
nn=30
this_palette_start %>% 
  bind_rows(
    tibble(r = random_channels(nn),
           g = random_channels(nn),
           b = random_channels(nn))
  ) %>% 
  distinct() %>% 
  mutate(col = rgb(r, g, b, maxColorValue = 255)) %>% 
  pull(col) -> this_palette 

this_palette %>% scales::show_col()

#Generate and plot all factors

tibble::tibble(number = 1:100) %>% 
  mutate(factors = purrr::map(number, get_prime_factors),
         num_factors = purrr::map_dbl(factors, length))  %>% 
  unnest(factors) %>% 
  add_row(number=1, factors=1, num_factors=1, .before = 1) -> prime_decomp

prime_decomp %>% 
  group_by(number) %>% 
  mutate(x_min = (row_number() - 1)/num_factors,
         x_max = (row_number() - 0)/num_factors,
         y_min = 0, y_max = 1) %>% 
  ungroup() %>% 
  mutate(number_f = factor(number, 
                           levels = as.character(rep(1:10, 10)+rep(9:0, each = 10)*10))) %>% 
  ggplot()+
  geom_rect(aes(xmin=x_min, xmax=x_max, ymin=y_min, ymax=y_max,
                fill = as.factor(factors)), color = "black") +
  scale_fill_manual(values = this_palette) +
  coord_fixed(expand=F, xlim=c(0,1), ylim=c(0,1))+
  facet_wrap(~number_f, nrow=10,
             strip.position = "bottom") +
  theme_void()+
  theme(
    legend.position = "none",
    panel.border = element_rect(fill = NA, size =1.5),
    panel.spacing = grid::unit(0, "cm"),
    strip.background = element_rect(color = "black")
  )