animation draft

[mdsumner]

library(dplyr)
library(raadtools)
library(SOmap)

ele <- SOmap_data$mirounga_leonina
polar_proj <- "+proj=stere +lat_0=-90 +lat_ts=-71 +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs +ellps=WGS84 +towgs84=0,0,0"
ele[c("x", "y")] <- rgdal::project(as.matrix(ele[c("lon", "lat")]), polar_proj)
## raadtools normalizes all dates to the temporal sequence of the env data
ice_raster <- readice(ele$date)
length(getZ(ice_raster))
range(getZ(ice_raster))
range(diff(getZ(ice_raster)))
roi <- round(c(range(ele$lon), range(ele$lat)) + c(-2, 2, -2, 2))
bx <- projectRaster(readtopo("etopo2", xylim = roi), raster(extent(range(ele$x) + c(-1, 1) * 5e5, range(ele$y) + c(-1, 1) * 5e5), 
                                                            nrows = 300, ncols = 300, crs = polar_proj))

# 15 % is a standard "ice edge" threshold
contour_raster_sf <- function(x, level = 15, date = as.POSIXct(NA, tz = "UTC")) {
  raster::rasterToContour(x, level = level, maxpixels = prod(dim(x[[1]]))) %>% 
    sf::st_as_sf() %>% dplyr::mutate(date = date)
}

ice_edge <- vector("list", nlayers(ice_raster))
for (i in seq_along(ice_edge)) {
  ice_edge[[i]] <- contour_raster_sf(ice_raster[[i]], date = getZ(ice_raster)[i])
}
ice_edge <- sf::st_cast(do.call(rbind, ice_edge), "MULTILINESTRING")

bathy_data <- as.data.frame(bx, xy = TRUE) %>% dplyr::filter(!is.na(z))
bathy_data$date <- NULL
library(gganimate)
g <- ggplot() + 
#  geom_raster(data = bathy_data, aes(x, y, fill = z)) + 
  geom_sf(data = ice_edge, colour = "black") + 
  geom_point(data = ele, aes(x, y,  colour = id)) + 
 theme_bw() + xlim(range(ele$x) + c(-1, 1) * 2e5) + ylim(range(ele$y) + c(-1, 1) * 2e5) + 
  transition_time(date)

##I"m finding this fails with geom_raster or geom_path used above
g

## suggested to fix problem when more time steps than frames
# gganimate::animate(g, detail = 3)

[mdsumner]

[raymondben]

Cooooooooooool! Tweaked a bit and added, https://github.com/AustralianAntarcticDivision/ropenblog/commit/3f7f2eaeddeb78f8c1905808b055b8f3e8d52b3a.