bookdown 错误“CTeX 字体集‘mac’在当前模式下不可用。”使用输出格式 pdf_book 和 pdf_document2 时

我正在使用“bookdown”RStudio, tinyTex and pandoc用中文写一份报告。因为我需要使用交叉引用，所以我必须将输出格式设置为“pdf_document2”，但我有一个问题CTeX fontest.

首先，这是 YAML 部分：

---
title: "title"
author:
  - author
documentclass: ctexart
site: bookdown::bookdown_site
output:
  bookdown::pdf_document2
bibliography: bib_v1.bib
csl: chinese-author-date.csl
link-citations: yes
colorlinks: yes
classoption: "hyperref,"
---

当我写这本书的时候出了点问题，上面写着

“CTeX 字体集‘mac’在当前模式下不可用。”

这是完整的错误信息：

tlmgr search --file --global '/mac'
TeX Live 2017 is frozen forever and will no
longer be updated.  This happens in preparation for a new release.

If you are interested in helping to pretest the new release (when
pretests are available), please read     http://tug.org/texlive/pretest.html.
Otherwise, just wait, and the new release will be ready in due time.
! Critical ctex error: "fontset-unavailable"
! 
! CTeX fontset 'mac' is unavailable in current mode.
! 
! See the ctex documentation for further information.
! 
! For immediate help type H <return>.
!...............................................  

! 
! CTeX fontset 'mac' is unavailable in current mode.
! 
! See the ctex documentation for further information.
! 
! For immediate help type H <return>.
!...............................................  

! CTeX fontset 'mac' is unavailable in current mode.
! 
! See the ctex documentation for further information.
! 
! For immediate help type H <return>.
!...............................................  

! 
! See the ctex documentation for further information.
! 
! For immediate help type H <return>.
!...............................................  

! See the ctex documentation for further information.
! 
! For immediate help type H <return>.
!...............................................  

! 
! For immediate help type H <return>.
!...............................................  

! For immediate help type H <return>.
!...............................................  

Error: Failed to compile _main.tex. See _main.log for more info.
In addition: Warning message:
In parse_packages(logfile, quiet = c(TRUE, FALSE, FALSE)) :
  Failed to find a package that contains mac
Please delete _main.Rmd after you finish debugging the error.
Execution halted

Exited with status 1.

我对 LaTeX 不熟悉，不知道如何解决这个问题。我尝试过建立bookdown-中文演示 https://github.com/yihui/bookdown-chinese到这里，就成功了。我也尝试在自己的文件中使用这个演示的模板，或者使用输出格式pdf_book，但我仍然遇到同样的问题。

那么我可以做些什么来解决它吗？

非常感谢您的帮助！

bookdown-chinese 演示使用 XeLaTeX：https://github.com/yihui/bookdown-chinese/blob/master/_output.yml#L22 https://github.com/yihui/bookdown-chinese/blob/master/_output.yml#L22你也可以这样做：

output: 
  bookdown::pdf_document2:
    latex_engine: xelatex