Column alignment in xtable output

Question

I'm using xtable to manage R output in Sweave. See code below:

CC <- data.frame(
    y = c(449, 413, 326, 409, 358, 291, 341, 278, 312)/12,
    P = ordered(gl(3, 3)), N = ordered(gl(3, 1, 9))
)
CC.aov <- aov(y ~ N * P, data = CC , weights = rep(12, 9))
Summary <- summary(CC.aov, split = list(N = list(L = 1, Q = 2),
                                        P = list(L = 1, Q = 2)))
Summary

            Df Sum Sq Mean Sq
N            2 1016.7   508.3
  N: L       1 1012.5  1012.5
  N: Q       1    4.2     4.2
P            2  917.4   458.7
  P: L       1  917.3   917.3
  P: Q       1    0.0     0.0
N:P          4  399.3    99.8
  N:P: L.L   1  184.1   184.1
  N:P: Q.L   1  152.1   152.1
  N:P: L.Q   1   49.0    49.0
  N:P: Q.Q   1   14.1    14.1

I like to indent the first column as shown in the output above. But when I use xtable(Summary) the first column is aligned left. I know how to align left, right or center but could not figure out how to get the output as indented in the first. Any help in this regard will be highly appreciated. Thanks

Answer 1

This example shows how to customize the table combining the use of the sanitize argument in xtable and the function \hskip in latex.

The code would be:

named = rownames(Summary[[1]])
tags= gsub("  "," ",named)
rownames(Summary[[1]])= c(ifelse(nchar(tags)<8,tags,paste("\\hskip .5cm",tags,sep=' ')))
print(xtable(Summary[[1]]), type="latex", sanitize.text.function = function(x){x})

EDIT: Following Dwin's suggestion of using

grepl("^ ", rownames(Summary[[1]])

That provides a more general solution. The code would change to:

named = rownames(Summary[[1]])
tags= grepl("^ ", rownames(Summary[[1]]))
rownames(Summary[[1]])= c(ifelse(tags==F,named,paste("\\hskip .5cm",named,sep=' ')))
print(xtable(Summary[[1]]), type="latex", sanitize.text.function = function(x){x})

Answer 2

Edit the output of xtable to add another column and put empty column dividers in from of the onew you want to indent: (and assuming appropriate document header and footer.)

\begin{tabular}{llrrr}
  \hline
& fac & Df & Sum Sq & Mean Sq \\ 
  \hline
N   &        & 2 & 1016.67 & 508.33 \\ 
 &  N: L      & 1 & 1012.50 & 1012.50 \\ 
 & N: Q      & 1 & 4.17 & 4.17 \\ 
P  &        & 2 & 917.39 & 458.69 \\ 
 &  P: L      & 1 & 917.35 & 917.35 \\ 
 &  P: Q      & 1 & 0.04 & 0.04 \\ 
N:P   &      & 4 & 399.28 & 99.82 \\ 
 & N:P: L.L  & 1 & 184.08 & 184.08 \\ 
 &N:P: Q.L  & 1 & 152.11 & 152.11 \\ 
 &N:P: L.Q  & 1 & 49.00 & 49.00 \\ 
 &N:P: Q.Q  & 1 & 14.08 & 14.08 \\ 
\hline
\end{tabular}