Cumulative animation where last frame is shown first

cumulative-last-first.R

accumulate_by <- function(dat, var, showLastFirst = FALSE) {
  var <- lazyeval::f_eval(var, dat)
  lvls <- plotly:::getLevels(var)
  dats <- lapply(seq_along(lvls), function(x) {
    cbind(dat[var %in% lvls[seq(1, x)], ], frame = lvls[[x]])
  })
  if (showLastFirst) {
    lastFrame <- dats[[length(dats)]]
    # you will likely have to fiddle with this value
    lastFrame$frame <- 0
    dats <- c(list(lastFrame), dats)
  }
  dplyr::bind_rows(dats)
}

df <- data.frame(
  x = c(1,2,3),
  y = c(1,2,3),
  f = c(1,2,3)
)

p <- df %>% 
  accumulate_by(~f, TRUE) %>%
  plot_ly(
    x = ~x,
    y = ~y,
    frame = ~frame,
    type = 'scatter',
    mode = 'markers',
    showlegend = F
  )