r-markdown和kableExtra pdf输出错误

---
title: "test_kableExtra"
date: "14/12/2018"
output: 
  pdf_document:
    latex_engine: xelatex
    includes:
      in_header: head.tex
---

``` {r table, echo = FALSE}
library(tidyverse)
library(kableExtra)

table <- tibble(`Column title` = "lots of very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very long text ")

kable(table, booktabs = T, caption = "Table title") %>%
  kable_styling(full_width = F) %>%
  column_spec(1, width = "5cm")

```

More text...

在头脑中。特克斯:

\usepackage{float}
\usepackage{booktabs}
\usepackage{longtable}
\usepackage{array}
\usepackage{multirow}
\usepackage{wrapfig}
\usepackage{colortbl}
\usepackage{pdflscape}
\usepackage{tabu}
\usepackage{threeparttable}
\usepackage{threeparttablex}
\usepackage[normalem]{ulem}
\usepackage{makecell}

我明白了 ! LaTeX Error: \caption outside float.

如果我移除 caption = "Table title"

然后我得到这个输出

我不明白为什么:

• 列宽未更改为5cm,

• 为什么代码块后的文本居中,

• 为什么“\begin{tab…”“\end{table}即将出现。

谢谢你的帮助!