ggplot shape = Unicode (e.g. arrows like "\u2198" or LaTeX \searrow)?

Question

I'd like to use Unicode shapes in ggplot2 geom_point() (specifically, arrows like ↘, Unicode "\u2198", or LaTeX \searrow), as in shape = "\u2198", that are not in the default font. In this unanswered post, @Laserhedvig commented "it seems that the problem lies in the font. Apparently, the base default fonts don't contain support for these specific glyphs. Now, how to change the font for the shape argument of geom_point()?"

This solution for Unicode in axes.text uses theme(axis.text.x = element_text(family = "FreeSerif")), and this solution uses theme(text=element_text(size=16, family="Comic Sans MS")) for all text, but how can I do this for shape?

1. Is there a general solution to use Unicode for shape? (must I somehow use cairo and/or a font family argument?)
2. If not, is there some other set of arrow shapes? (My search for arrow shapes and glyphs, including in the scale_shape documentation came up empty.)

In my case, I need a ggplot2 layer showing qualitative predictions for the direction of change at points in time across discrete categories.

An example:

library(dplyr)
library(ggplot2)

d <- tibble(year = c(1, 1, 2, 2),
       policy = rep( c('policy 1', 'policy 2'), 2),
       prediction = c(NA, 'increase', 'decrease', NA),
       predictionUnicode = c(NA, '\u2197', '\u2198', NA))

ggplot(d) + 
  geom_point(aes(x = year, y = policy, color = prediction), shape = "\u2198")

shape = "\u2198" (i.e. "↘") does not work

Edit: Thanks to djangodude's comment about ggplot's font usage, I found the family argument of geom_text, which allows different fonts. Thus, Unicode "shapes" can be plotted as characters with geom_text. However, the legend for geom_text is fixed to "a". And themes only control non-data display, so the base_family argument will not work for shape.

ggplot(d) + 
  geom_tile( aes(x = year, y = policy), color = "black", fill = "white") +   
  # geom_point does not allow new fonts?
  geom_point(aes(x = year, y = policy, 
                 color = prediction), shape = "\u2198") + 
  # geom_text does allow new fonts, but the legend text is fixed to "a"
  geom_text(aes(x = year, y= policy, 
                color = prediction,
                label = predictionUnicode), 
            family = "Calibri") + 
  scale_x_continuous(breaks = c(1,2)) +
  theme_gray(base_family = "Calibri") 

geom_text plots unicode, but not in the legend

It seems the shape argument is really the correct way to do this, right?

I tried setting Sys.setenv(LANG = "en_US.UTF-8") and Sys.setenv(LANG = "Unicode") to no effect, but perhaps some global language setting would affect shape?

Thank you so much for any help!

Note: These solutions for Unicode skull and crossbones and half-filled points do not have legends and will not work without the right font:

To get the right font:

1. Look for an installed font that contains the Unicode character you seek. I found these instructions helpful.

2. Import installed fonts into R

library(extrafont)
font_import()
fonts()

sessionInfo()
R version 3.5.2 (2018-12-20)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS Mojave 10.14.3

Answer 1

Use shape="\u2198" instead of \u8600. When specifying a character with \u notation, the value needs to be hexadecimal. 8600 is the decimal value for Unicode character LOWER RIGHT ARROW; the hex value is 2198.