insert image into ggplot + gganimate when x axis are dates

Question

I want to animate some data using gganimate. Taking an example from their github page I changed it a bit to reflect my case. X-axis are dates and I want a logo in the same position for all frames.

Reproducible code:

library(magick)
library(gapminder)
library(ggplot2)
library(rsvg)
library(gganimate)

tiger <- image_read_svg('http://jeroen.github.io/images/tiger.svg', width = 400)

(p <- ggplot(gapminder, aes(year, lifeExp, size = pop, colour = country)) +
  geom_point(alpha = 0.7, show.legend = FALSE) +
  scale_colour_manual(values = country_colors) +
  scale_size(range = c(2, 12)) +
  scale_x_log10() +
  annotation_raster(tiger, ymin = 75, ymax = 100, xmin = 1965, xmax = 2005) )

# here the animate part (not needed just for ilustrative purposes)

p + labs(title = 'Year: {frame_time}', x = 'Year', y = 'life expectancy') +
  transition_time(year) +
  ease_aes('linear')

The issue is I can plot the logo in any chart when x-axis are not dates.

I suspect this issue is related to date type but no success so far.

Answer 1

Your issue appears to relate to the log scale you are calling for your x-axis. It's taking your year vector — which is not a date, rather a 4-digit integer — and applying a log transformation to it... which as @camille has pointed out means that when you are calling animation_raster the coordinates (xmin / xmax) are off the plot grid.

Here's a solution that incorporates dates by changing the year in your data frame to a date format. It also layers the image behind the geoms and renders in its original scale ie. 1x1.

library(magick) 
library(gapminder)
library(ggplot2)
library(rsvg)
library(gganimate)
library(lubridate)

tiger <- image_read_svg('http://jeroen.github.io/images/tiger.svg', width = 
400)

xmin <- ymd("1965/01/01")
xmax <- ymd("2005/01/01")
ymin <- 30
height <- round(as.numeric(xmax-xmin)/356, 0)
ymax <- ymin + height

gapminder %>%
    mutate(year = ymd(year, truncated = 2L)) %>%
    ggplot() +
    aes(year, lifeExp, size = pop, colour = country) +
    annotation_raster(tiger, ymin = ymin, ymax = ymax, xmin = xmin, xmax = 
    xmax) +
    geom_point(alpha = 0.7, show.legend = FALSE) +
    scale_colour_manual(values = country_colors) +
    scale_size(range = c(2, 12)) +
    labs(title = 'Year: {frame_time}', x = 'Year', y = 'life expectancy') +
    transition_time(year) +
    ease_aes('linear') +
    anim_save("animated_tiger_timeseries.gif")

Which produces this...

Is this what you are looking for?