I tried to produce a gganimation with two geoms on a map of germany, but eventually only produced a blank animation. This here is a reproducible example of the animation I tried to produce:

# Load necessary packages
pacman::p_load(ggplot2, tidyverse, maps, mapdata,
               gganimate, av, emojifont)

# Production of example data
{
set.seed(123)
index = rep(c(1:10),
            each = 100) ; year = rep(c(1951:1960), 
                                     each = 10, times = 10); month = rep(c(1:10),
                                                                         each = 1,
                                                                         times = 100)

variable_of_interest = runif(1000,
                      min = 0,
                      max = 0.4); season = rep(x = c("Winter", "Winter", "Spring", "Spring", "Spring",
                                                     "Summer", "Summer", "Summer", "Autmn", "Autmn"),
                                               times = 100)

lat = rep(c(seq(from = 48,
              to = 53,
              length = 10)),
          each = 100); lon = rep(c(seq(from = 7,
                                       to = 14,
                                       length = 10)),
                                 each = 100)

Variable_of_Interest = as.data.frame(cbind(index, year, month, variable_of_interest, season, lat, lon))

Variable_of_Interest$month_of_year = paste0(Variable_of_Interest$year,
                                                        "-",
                                                        Variable_of_Interest$month)

#Variable_of_Interest = Variable_of_Interest[order(Variable_of_Interest$year,
#                                                                              Variable_of_Interest$month),]

rownames(Variable_of_Interest) = NULL
}

# Transform columns from character to numeric
Variable_of_Interest = mutate_at(Variable_of_Interest,
                                               c(1,2,3,4,6,7),
                                               as.numeric)


# Preperation for the animation
season_symbols = c("Spring" = emoji("cherry_blossom"),
                   "Summer" =  emoji("tropical_drink"), 
                   "Autmn" = emoji("fallen_leaf"),
                   "Winter" = emoji("snowflake"))


# Map of values of the variable of interest
Variable_of_Interest_Map = ggplot(Variable_of_Interest)   
  geom_path(data = map_data("world","Germany"),
            aes(x = long, 
                y = lat, 
                group = group))  
  coord_fixed(xlim = c(6,
                       15),
              ylim = c(47,
                       55))   
  geom_point(aes(x=lon, 
                 y=lat, 
                 group = month_of_year,
                 shape = season), 
             size = 10)   
  scale_shape_manual(values = season_symbols, breaks = c("Spring", "Summer", "Autmn", "Winter"))  
  geom_point(aes(x=lon, 
                 y=lat, 
                 group = month_of_year),
             colour = ifelse(test = Variable_of_Interest$variable_of_interest > 0.3, 
                             I("red"),
                             I("blue")))   
  # scale_color_gradient(low="blue", high="yellow")   
  xlab("Longitude (degree)")  
  ylab("Latitude (degree)")   
  theme_bw()  
  transition_manual(frames = month_of_year)   
  theme(legend.position = "bottom", 
        legend.title = element_text(size=12, face="bold"),
        panel.background = element_blank(),
        legend.background = element_blank())  
  labs(title = '{unique(Variable_of_Interest$month_of_year)[as.integer(frame)]}', 
       color = paste0("Variable of Interest"),
       shape = "season")

anim_save("Variable-of-Interest.mp4",
          animate(
            Variable_of_Interest_Map,
            nframes = 1000,
            renderer = ffmpeg_renderer()
          ))

The plan was to draw a map of germany, use one set of geom_points to represent the variation of the variable_of_interest among the locations in Germany through time and another set of geom_points to visualize the present season through drawing symbols like snowflakes for winter.

CodePudding user response：

The main issue with your code is that you tried to display your emojis via the shape aes and a geom_point which at least on my machine resulted in an error. Also I have not found any reference on using emoji font like that. Instead you could achieve your desired result using a geom_text to which end I added a column to your data containing the season symbol and which could be mapped on the label aes:

library(tidyverse)
library(emojifont)
library(gganimate)

Variable_of_Interest$season_symbol <- season_symbols[Variable_of_Interest$season]

Variable_of_Interest_Map <- ggplot(Variable_of_Interest)  
  geom_path(
    data = map_data("world", "Germany"),
    aes(
      x = long,
      y = lat,
      group = group
    )
  )  
  coord_fixed(
    xlim = c(
      6,
      15
    ),
    ylim = c(
      47,
      55
    )
  )  
  geom_text(
    aes(
      x = lon,
      y = lat,
      group = month_of_year,
      label = season_symbol
    ),
    size = 10, family = "EmojiOne"
  )  
  geom_point(aes(
    x = lon,
    y = lat,
    colour = ifelse(variable_of_interest > 0.3, "red", "blue"),
    group = month_of_year
  ))  
  scale_color_manual(values = c(red = "red", blue = "blue"), guide = "none")  
  xlab("Longitude (degree)")  
  ylab("Latitude (degree)")  
  theme_bw()  
  transition_manual(frames = month_of_year)  
  theme(
    legend.position = "bottom",
    legend.title = element_text(size = 12, face = "bold"),
    panel.background = element_blank(),
    legend.background = element_blank()
  )  
  labs(
    title = "{unique(Variable_of_Interest$month_of_year)[as.integer(frame)]}",
    color = paste0("Variable of Interest"),
    shape = "season"
  )

Variable_of_Interest_Map