tiles.R

library(ggplot2)
library(tidyr)
library(viridis)

df <- data.frame(x = 1:10, y = 1:10) %>% expand(x, y) %>% mutate(n = as.integer(runif(min = 0, max = 26, n = 100)))

pal <- c(viridis(n = 23), "black", "purple", "pink")

ggplot(df, aes(x, y, fill = factor(n))) +
  geom_tile() +
  scale_fill_manual(values = pal, breaks = 0:25)