Bug of striped table when there are two sets of grouped columns

[stla]

Hello,
The Rnw file below produces an unexpected result.

\documentclass[table]{article}
\usepackage{longtable}
\usepackage{booktabs}
\usepackage{xcolor}

\begin{document}

<<>>=
library(knitr)
library(kableExtra)
options(knitr.table.format = "latex")
dat <- rbind(mtcars, mtcars)
@

<<results='asis'>>=
kable(dat, booktabs=TRUE, longtable=TRUE, 
      caption="A long striped table") %>%
  add_header_above(c(" ", "Group" = 5, " ", "Other Group" = 5)) %>%
  kable_styling(latex_options = c("striped", "repeat_header"))
@

\end{document}

There are two problems. Firstly, the second line of the header on the first page is colored:

Secondly, on the second page the caption and the first line of the header are colored:

Below is the generated LaTeX code:

\rowcolors{2}{white}{gray!6}

\begin{longtable}[t]{lrrrrrrrrrrr}
\caption{\label{tab:unnamed-chunk-2}A long striped table}\\
\toprule
\multicolumn{1}{c}{ } & \multicolumn{5}{c}{Group} & \multicolumn{1}{c}{ } & \multicolumn{5}{c}{Other Group} \\
\cmidrule(l{2pt}r{2pt}){2-6} \cmidrule(l{2pt}r{2pt}){8-12}
  & mpg & cyl & disp & hp & drat & wt & qsec & vs & am & gear & carb\\
\midrule
\endfirsthead
\caption{\label{tab:unnamed-chunk-2}A long striped table \textit{(continued)}}\\
\toprule
\multicolumn{1}{c}{ } & \multicolumn{5}{c}{Group} & \multicolumn{1}{c}{ } & \multicolumn{5}{c}{Other Group} \\
\cmidrule(l{2pt}r{2pt}){2-6} \cmidrule(l{2pt}r{2pt}){8-12}
  & mpg & cyl & disp & hp & drat & wt & qsec & vs & am & gear & carb\\
\midrule
\endhead
Mazda RX4 & 21.0 & 6 & 160.0 & 110 & 3.90 & 2.620 & 16.46 & 0 & 1 & 4 & 4\\
Mazda RX4 Wag & 21.0 & 6 & 160.0 & 110 & 3.90 & 2.875 & 17.02 & 0 & 1 & 4 & 4\\
Datsun 710 & 22.8 & 4 & 108.0 & 93 & 3.85 & 2.320 & 18.61 & 1 & 1 & 4 & 1\\
Hornet 4 Drive & 21.4 & 6 & 258.0 & 110 & 3.08 & 3.215 & 19.44 & 1 & 0 & 3 & 1\\
Hornet Sportabout & 18.7 & 8 & 360.0 & 175 & 3.15 & 3.440 & 17.02 & 0 & 0 & 3 & 2\\
\addlinespace
Valiant & 18.1 & 6 & 225.0 & 105 & 2.76 & 3.460 & 20.22 & 1 & 0 & 3 & 1\\
Duster 360 & 14.3 & 8 & 360.0 & 245 & 3.21 & 3.570 & 15.84 & 0 & 0 & 3 & 4\\

[stla]

In case if this is a LaTeX issue, I've opened the issue on tex.stackexchange: https://tex.stackexchange.com/questions/384100/bug-with-striped-long-table-when-there-are-two-groups-of-columns.

[stla]

The LaTeX solution posted by Ulrike Fisher works, using hiderowcolors and showrowcolors:

\begin{longtable}[t]{lrrrrrrrrrrr}
\hiderowcolors
\caption{A long striped table}\\
\toprule
\multicolumn{1}{c}{ } & \multicolumn{5}{c}{Group} & \multicolumn{1}{c}{ } & \multicolumn{5}{c}{Other Group} \\
\cmidrule(l{2pt}r{2pt}){2-6} \cmidrule(l{2pt}r{2pt}){8-12}
 & mpg & cyl & disp & hp & drat & wt & qsec & vs & am & gear & carb\\
\midrule
\endfirsthead
\hiderowcolors
\caption{A long striped table \textit{(continued)}}\\
\toprule
\multicolumn{1}{c}{ } & \multicolumn{5}{c}{Group} & \multicolumn{1}{c}{ } & \multicolumn{5}{c}{Other Group} \\
\cmidrule(l{2pt}r{2pt}){2-6} \cmidrule(l{2pt}r{2pt}){8-12}
  & mpg & cyl & disp & hp & drat & wt & qsec & vs & am & gear & carb\\
\midrule
\endhead
\showrowcolors
Mazda RX4 & 21.0 & 6 & 160.0 & 110 & 3.90 & 2.620 & 16.46 & 0 & 1 & 4 & 4\\
.........

[stla]

This works like this:

<<results='asis'>>=
x <- kable(dat, booktabs=TRUE, longtable=TRUE, 
      caption="A long striped table") %>%
  add_header_above(c(" ", "Group"=5, " ", "Other Group" = 5)) %>%
  kable_styling(latex_options = c("striped", "repeat_header"))
sub("\\\\endhead", "\\\\endhead\\\\showrowcolors", gsub("\\\\toprule", "\\\\hiderowcolors\\\\toprule", x))
@

So I believe you can fix the function styling_latex_striped like this:

styling_latex_striped <- function(x, table_info) {
  # gray!6 is the same as shadecolor ({RGB}{248, 248, 248}) in pdf_document
  if (table_info$tabular == "longtable" & !is.na(table_info$caption)) {
    row_color <- "\\rowcolors{2}{white}{gray!6}\n"
  } else {
    row_color <- "\\rowcolors{2}{gray!6}{white}\n"
  }
  x <- sub("\\\\endhead", "\\\\endhead\\\\showrowcolors", gsub("\\\\toprule", "\\\\hiderowcolors\\\\toprule", x))
  return(paste0(row_color, x, "\n\\rowcolors{2}{white}{white}"))
}

[haozhu233]

Awesome! Thank you so much for doing this! I will make a fix later today.

[stla]

Great. Thanks. And big thanks for this nice package!

[haozhu233]

I put in some extra codes to control the behavior in all conditions. Thank you @stla for making it happening!