Adding a horizontal line between the rows in a latex table using R xtable

Question

I have a sample latex table generation code like this

df<-data.frame(name=rep(letters[1:7],each=24),salary=runif(24*7,100,200))
lst<-tapply(df$salary,df$name,matrix,nrow=4,byrow=T)
xlst<-lapply(lst,xtable)

Now I want to introduce \hdashline automatically after every row in every table and also a \vspace{2em} in between the tables from R code Wat I have tried is this

for(i in seq_along(lst)){
  addtorow[i] <- list(pos = list(seq_len(nrow(lst[[i]])-1)),
                      command = "\\hdashline \n")
}

wat changes do i need to make in for loop..It works when I apply for a single table but not working in a for loop...Any help is much appreciated...

Answer 1

Rather than using a loop, consider using the existing print.xtable functionality combined with paste.

1. hdashlines: Consider using the print.xtable parameters. For example, there is a parameter hline.after that controls horizontal lines between the table lines.

2. vspace: This is possibly simpler using paste.

For example:

library(xtable)
df <- data.frame(name=rep(letters[1:3],each=24),salary=runif(24*3,100,200))
lst <- tapply(df$salary,df$name,matrix,nrow=4,byrow=T)
xlst <- lapply(lst,function(x)print(xtable(x), hline.after=1:nrow(x)))
xlst <- lapply(xlst, paste, "\\vspace{2em}")
xlst

[1] "% latex table generated in R 2.13.1 by xtable 1.5-6 package\n% Tue Aug 23 13:36:41 2011\n\begin{table}[ht]\n\begin{center}\n\begin{tabular}{rrrrrrr}\n & 1 & 2 & 3 & 4 & 5 & 6 \\ \n 1 & 158.66 & 115.81 & 106.70 & 128.78 & 157.43 & 191.01 \\ \n \hline\n2 & 159.09 & 172.31 & 153.93 & 127.91 & 106.93 & 147.95 \\ \n \hline\n3 & 135.65 & 139.45 & 192.90 & 108.78 & 186.52 & 164.10 \\ \n \hline\n4 & 190.10 & 154.39 & 124.91 & 199.24 & 161.99 & 167.61 \\ \n
\hline\n\end{tabular}\n\end{center}\n\end{table}\n \vspace{2em}"

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See ?print.xtable for more details. If hline.after is not flexible enough for your purposes, then have a look at add.to.row where you can specify both the position and exact element type to add.