RMarkdown not printing Chinese characters in graphs - r

Question

---
title:
output:
pdf_document:
latex_engine: xelatex
fontsize: 11pt
#mainfont: Calibri
classoption: letter
geometry: left=0.5in, right=0.5in, top=0.6in, bottom=1.25in
subparagraph: yes
header-includes:
- \usepackage[UTF8]{ctex}
- \usepackage{setspace}
- \usepackage{tocloft}
- \usepackage{anyfontsize}
- \usepackage{fancyhdr}
- \usepackage{fontspec}
- \usepackage{sectsty}
- \sectionfont{\huge}
- \subsectionfont{\fontsize{14}{16.8}\selectfont}
- \pagestyle{fancy}
- \renewcommand{\headrulewidth}{0pt}
---
```{r}
library(ggplot2)
print("中文")
df <- data.frame(
gp = factor(rep(letters[1:3], each = 10)),
y = rnorm(30)
)
ds <- plyr::ddply(df, "gp", plyr::summarise, mean = mean(y), sd = sd(y))
# The summary data frame ds is used to plot larger red points on top
# of the raw data. Note that we don't need to supply `data` or `mapping`
# in each layer because the defaults from ggplot() are used.
ggplot(df, aes(gp, y)) +
geom_point() +
geom_point(data = ds, aes(y = mean), colour = 'red', size = 3) +
labs(x = "中文")
```
After knitting this file, it seems that the character encoding works fine for the print function, but the Chinese characters do not show up in graph labels, and I get errors on character conversions. I am a Mac user.

Answer 1

TL;DR: This doesn't appear to be a knitr/rmarkdown issue, but rather an issue related to both the font and the output device. I'm not sure of the cause, but the workaround below involves changing the output font (Batang worked for me) and the output device (pdf is the default, but changing to cairo_pdf or png both worked for me).
First, identify a font family for which R will render the characters properly. I'm not sure in general how to determine this without trial and error, but in the past I've found that the Symbola and Batang fonts often seem to work with non-English characters and various unicode symbols. You'll need to install the fonts on your computer if you don't have them, and you also might need to use the extrafont package to register the fonts in R. Then you can run the plot code in the console and see if the Chinese characters render properly.
With the Batang font, I found that I was able to output plots to the console with the Chinese characters rendered properly. However, the standard pdf device failed to render the characters, whether saving the plot to pdf interactively or when knitting. Instead I tried the cairo_pdf and png devices and these both worked. Here's example code (using the same yaml as in your question):
```{r, include=FALSE}
knitr::opts_chunk$set(echo=FALSE)
library(ggplot2)
```
```{r, dev="cairo_pdf"}
df <- data.frame(
gp = factor(rep(letters[1:3], each = 10)),
y = rnorm(30)
)
ds <- plyr::ddply(df, "gp", plyr::summarise, mean = mean(y), sd = sd(y))
ggplot(df, aes(gp, y)) +
geom_point() +
geom_point(data = ds, aes(y = mean), colour = 'red', size = 3) +
labs(x = "中文", title="cairo_pdf device") +
#theme(axis.title.x=element_text(family="Batang")) # To change font only for x-axis title
theme(text=element_text(family="Batang", size=15))
```
```{r, dev="png", dpi=400}
ggplot(df, aes(gp, y)) +
geom_point() +
geom_point(data = ds, aes(y = mean), colour = 'red', size = 3) +
labs(x = "中文", title="png device") +
theme(text=element_text(family="Batang", size=15))
```
And here's what the plots look like in the output document: