gganimate: two layers with different geometries and timepoints

Question

The problem is similar to this question but here the two layers use different geometries, geom_tile and geom_point. The idea is to have tiles show up at different locations only in frames 2, 5, 8, and the point move along the diagonal in every frame.

When trying to run the following example, I get the error:

Error: time data must be the same class in all layers

Example

require(data.table)
require(ggplot2)
require(gganimate)

# 3 tiles along x = 10-y; present at time points 2, 5, 8
dtP1 = data.table(x = c(1, 5, 9),
                  y = c(9, 5, 1),
                  t = c(2, 5, 8))

# 9 points along x=y; present at every time point
dtP2 = data.table(x = 1:9,
                  y = 1:9,
                  t = 1:9)

p = ggplot() +
    geom_tile(data = dtP1,
              aes(x = x,
                  y = y),
                  color = "#000000") +
    geom_point(data = dtP2,
               aes(x = x,
                   y = y),
               color = "#FF0000") +
    gganimate::transition_time(t) +
    gganimate::ease_aes('linear')

pAnim = gganimate::animate(p, 
                           renderer = av_renderer("~/test.mp4"), 
                           fps = 1, 
                           nframes = 9,
                           height = 400, width = 400)

Answer 1

Does the following work for you?

library(dplyr)

p <- rbind(dtP1 %>% mutate(group = "group1"),
           dtP2 %>% mutate(group = "group2")) %>%
  tidyr::complete(t, group) %>%
  ggplot(aes(x = x, y = y)) +
  geom_tile(data = . %>% filter(group == "group1"),
            color = "black") +
  geom_point(data = . %>% filter(group == "group2"),
             color = "red") +
  ggtitle("{frame_time}") + # added this to show the frame explicitly; optional
  transition_time(t) +
  ease_aes('linear')

animate(p, nframes = 9, fps = 1)