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I am following this example in an attempt to add highlighting to rows of a LaTeX table created by xtable. In my version, I want to add highlighting to rows conditional upon column c having a value of 1. Here's my R code to generate the table.

<<example>>=
# create data frame
  my.df=data.frame(a=c(1:10),b=letters[1:10],c=sample(c(0,1), 10, replace=TRUE))

# identify index of rows to highlight
  row.i.1 <- which(my.df$c==1)

print(xtable(my.df),
      only.contents=TRUE,
      include.rownames=FALSE,
      include.colnames=FALSE,
      hline.after=NULL,
      type="latex",
      add.to.row=list(
            pos=list(as.list(row.i.1))[[1]],
            command=rep("\\rowcolor{green!20!white}",
                        length(seq(from=1,to=length(row.i.1),by=1)))),
      sanitize.text.function=identity
      )
@

This produces the following table:

% latex table generated in R 3.0.1 by xtable 1.7-1 package
% Mon Nov 11 23:31:51 2013
   1 & a & 1.00 \\ 
   \rowcolor{green!20!white}  2 & b & 1.00 \\ 
   \rowcolor{green!20!white}  3 & c & 1.00 \\ 
   \rowcolor{green!20!white}  4 & d & 0.00 \\ 
    5 & e & 1.00 \\ 
   \rowcolor{green!20!white}  6 & f & 0.00 \\ 
    7 & g & 0.00 \\ 
    8 & h & 1.00 \\ 
   \rowcolor{green!20!white}  9 & i & 0.00 \\ 
   10 & j & 1.00 \\ 
   \rowcolor{green!20!white}

As you can see, the \rowcolors are shifted down by 1 row. It should be:

   \rowcolor{green!20!white}  1 & a & 1.00 \\ 
   \rowcolor{green!20!white}  2 & b & 1.00 \\ 
   \rowcolor{green!20!white}  3 & c & 1.00 \\ 
    4 & d & 0.00 \\ 
   \rowcolor{green!20!white}  5 & e & 1.00 \\ 
    6 & f & 0.00 \\ 
    7 & g & 0.00 \\ 
   \rowcolor{green!20!white}  8 & h & 1.00 \\ 
    9 & i & 0.00 \\ 
   \rowcolor{green!20!white}  10 & j & 1.00 \\

What is causing this? I have a few extras in my print(xtable()) command to fit my situation, but I don't think they matter for this example.

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Eric Green
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1 Answers1

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This works for me. Notice that I substracted one from pos values.

print(xtable(my.df),
      only.contents=TRUE,
      include.rownames=FALSE,
      include.colnames=FALSE,
      hline.after=NULL,
      type="latex",
      add.to.row=list(
        pos=list(as.list(row.i.1-1))[[1]],
        command=rep("\\rowcolor{green!20!white}",
                    length(seq(from=1,to=length(row.i.1),by=1)))),
      sanitize.text.function=identity
)
Roman Luštrik
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  • thanks, @Roman. it works for me too, but i don't see why the subtraction is needed. but it works, so i will use and be thankful. if anyone sees another approach that works without this fix, i'd be interested to know the answer. but in the meantime, thanks again. gets the job done nicely. – Eric Green Nov 12 '13 at 12:54
  • @EricGreen Maybe your assumption is wrong about the `pos` argument. The positions perhaps denote _after_ which line the `command` is parsed... – Roman Luštrik Nov 12 '13 at 23:52
  • @roman-lustrik You are correct, and an added benefit of using that way of counting is that xtable can put stuff before `\begin{tabular}` (pos = -1), or immediately after `\begin{tabular}` (pos = 0), or immediately after the first row (pos = 1, say a `\toprule` command...). – solarchemist Nov 13 '13 at 17:56