Visualise a sorting algorithm

sortviz.R

library(ggplot2)
library(dplyr)

# make starting vector 
A = LETTERS[5:1]

# pre-allocate matrix to store steps
n = length(A)
steps <- matrix(nrow = (n*n)+1,
                ncol = 2 + n)
steps[1, ] = c(0, 0, A)

# iterate
for (i in 1:n) {
  for (j in 1:n) {
    if (A[i] < A[j]){
      Ai = A[i]; Aj = A[j]
      A[i] = Aj; A[j] = Ai
    }
    steps[(i-1)*n + j+1,] = c(i, j, A)
  }
}

# get matrix to long df
steps_df <- as.data.frame(steps)
names(steps_df) = c("i", "j", paste0("pos_", 1:n))
steps_df$step = 1:nrow(steps_df)-1
steps_df = tidyr::pivot_longer(steps_df, 
                        cols = starts_with("pos_"),
                        names_to = "position",
                        names_prefix = "pos_",
                        values_to = "value",
                        names_transform = list(position = as.integer))

# bump plot
ggplot(data = steps_df, 
       mapping = aes(x = step, 
                     y = position, 
                     label = value,
                     colour = value)) +
  ggbump::geom_bump(size = 4, alpha = 0.5) +
  geom_text(data = filter(steps_df, step == max(step)),
            color = "black", 
            hjust = 0, nudge_x = 0.2) +
  geom_text(data = filter(steps_df, step == min(step)),
            color = "black", 
            hjust = 1, nudge_x = -0.2) +
  scale_y_reverse(breaks = 1:n, 
                  expand = expansion(.2)) +
  theme(legend.position = "none")