ggplot: legend for emojis in plot

Question

The following code produces a chart with emojis instead of point shapes.

library(tidyverse)
library(emojifont)
load.emojifont("OpenSansEmoji.ttf")

pal <- c("\U1f337"="blue","\U1f370"="red")
set.seed(124)
xdf <- data_frame(x=rnorm(10),y=rnorm(10),
                  label=rep(c("\U1f337","\U1f370"),5))
xdf %>% ggplot(aes(x=x,y=y,label=label,color=factor(label))) +
  geom_text(family="OpenSansEmoji") +
  scale_color_manual("object",values=pal) +
  guides(color=guide_legend(labels=FALSE)) +
  theme(legend.text=element_text(family="OpenSansEmoji"))

It is easy to see that the legend as informative as it could be. It would be nice to have colored emojis instead of twice the colored letter a, and instead of the black emojis, I would like to have the words tulip and cake.

Can this be accomplished?

Answer 1

I haven't worked much with emoji fonts before, but does the following work for you?

Data wrangling (I prefer to rename the label column to symbol for convenience, to keep their intended usages separate, but your mileage may vary):

xdf2 <- xdf %>%
  rename(symbol = label) %>%
  mutate(label = ifelse(symbol == "\U0001f337", "tulip", "cake"))

> xdf2
# A tibble: 10 x 4
         x      y symbol       label
     <dbl>  <dbl> <chr>        <chr>
 1 -1.39    0.318 "\U0001f337" tulip
 2  0.0383 -1.42  "\U0001f370" cake 
 3 -0.763  -0.405 "\U0001f337" tulip
 4  0.212   0.995 "\U0001f370" cake 
 5  1.43    0.959 "\U0001f337" tulip
 6  0.744   0.918 "\U0001f370" cake 
 7  0.700  -0.151 "\U0001f337" tulip
 8 -0.229  -1.22  "\U0001f370" cake 
 9  0.197  -0.869 "\U0001f337" tulip
10  1.21   -1.04  "\U0001f370" cake 

Plot:

xdf2 %>%
  ggplot(aes(x = x, y = y, shape = symbol, color = label)) +
  geom_point() +
  scale_shape_identity() +
  scale_color_manual(values = c("tulip" = "blue",
                                "cake" = "red"),
                     guide = guide_legend(
                       override.aes = list(shape = c("\U0001f370",
                                                     "\U0001f337"))
                     ))

(The actual tulip / cake emojis on my machine look different, for some reason...)