在ggplot中使用unicode符号

Question

当我在R界面中打印ggplot时,某些unicode符号有效,而当我将它们打印为pdf时,其他符号可以正常工作.我想了解这个过程.例如:

library(tidyverse)
library(magrittr)
library(showtext)

d1 <- data.frame(
  yvar = letters[1:3] %>% 
    rep(each = 4),
  xvar = LETTERS[1:4] %>% 
    rep(times = 3),
  ev = sample(1:4, size = 12, replace = T)
   ) %>%
  tbl_df %>% 
  modify(factor)

p1 <- d1 %>% 
  ggplot(
    aes(xvar, yvar, shape = ev)
  ) +
  geom_point(size = 8)  +
  scale_shape_manual(values=c("\u25BA","\u25D0","\u25BC","\u25B2"))

p1

版画

如果我将图打印为pdf,在启用Open Sans字体后,我会看到这一点

showtext.auto()
ggsave(
  "plot 1.pdf", 
  p1,
  width = 4,
  height = 2
  )

如何启用最大数量的unicode符号ggplot2？

(编辑:我的系统信息)

R version 3.5.1 (2018-07-02)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

Matrix products: default

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252    LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                           LC_TIME=English_United States.1252