unable to change the colors of the xtable cells in rmarkdown output to pdf

问题

I have this r markdown code:

---
header-includes:
   - \usepackage{xcolor, colortbl}
output:
    pdf_document:
      latex_engine: xelatex

---



```{r, results="asis"}

library(xtable)
library(formattable)
# Your data
tab = data.frame(category = c("A","B","C"), groupA = c(.2,.3,.5), groupB= c(.6,.7,.9))

# Function to cut your data, and assign colour to each range
f <- function(x) cut(x, c(0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, Inf), 
                      labels=c("green", "red", "blue", "orange", "yellow", "purple", "brown", "white"),
                      include.lowest = FALSE, right = TRUE)

# Apply function to columns: this overwrites your data
tab[c("groupA", "groupB")] <- lapply(tab[c("groupA", "groupB")], function(x)
                                            paste0("\\cellcolor{", f(x), "}", x))
# Sanitise output 
print(xtable(tab), sanitize.text.function = identity)
```

I need to color code the cells of the table.

I am getting this error:

output file: test.knit.md

! LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.1 <

pandoc.exe: Error producing PDF from TeX source
Error: pandoc document conversion failed with error 43
In addition: Warning message:
running command '"C:/Program Files/RStudio/bin/pandoc/pandoc" +RTS -K512m -RTS test.utf8.md --to latex --from markdown+autolink_bare_uris+ascii_identifiers+tex_math_single_backslash --output test.pdf --template "C:\Users\e598140\Documents\R\win-library\3.2\rmarkdown\rmd\latex\default.tex" --highlight-style tango --latex-engine xelatex --variable graphics=yes --variable "geometry:margin=1in"' had status 43 
Execution halted

Any ideas what is the issue here?

来源：https://stackoverflow.com/questions/44373073/unable-to-change-the-colors-of-the-xtable-cells-in-rmarkdown-output-to-pdf