strange symbols generated from rmarkdown when I use Chinese characters in ggplot2 - r

Question

Recently, I encounter a problem in Rmarkdown.
When I add Chinese characters into xlab() and ylab() in ggplot2. The pdf document generated by rmd will display strange ...... symbol. However, I try to search useful something and the result told me I should add dev: cairo_pdf. Ok, after I add the code to YAML, the new error strange symbols occur again. It displays another strange symbols of □□□.
I want to ask for help from someone who may pay attention to my quesiton. Could you help me? Thank you very much. And here my test code:
---
title: "test.Rmd"
author: "author"
documentclass: ctexart
output:
rticles::ctex:
fig_caption: yes
number_sections: yes
toc: no
dev: cairo_pdf
word_document: default
keywords:
header-includes: \usepackage{booktabs} \usepackage{longtable} \usepackage{array} \usepackage{multirow}
\usepackage{wrapfig} \usepackage{float} \floatplacement{figure}{H}
---
library(ggplot2)
ggplot(cars,aes(speed,dist)) +
geom_line()+xlab("速度\nSpeed") + ylab("距离\nDist")

Answer 1

Sorry, I cannot replicate your images. I just altered the header-includes and included the figure in a code chunk. Did you install xelatex and TeX Live?
Here is the code that worked fine for me:
---
title: "test.Rmd"
author: "author"
documentclass: ctexart
output:
rticles::ctex:
fig_caption: yes
number_sections: yes
toc: no
dev: cairo_pdf
word_document: default
header-includes:
- \usepackage{booktabs}
- \usepackage{longtable}
- \usepackage{array}
- \usepackage{multirow}
- \usepackage{wrapfig}
- \usepackage{float}
- \floatplacement{figure}{H}
---
```{r}
library(ggplot2)
ggplot(cars,aes(speed,dist)) +
geom_line()+xlab("速度\nSpeed") + ylab("距离\nDist")
```
-output