begin{table}[ht]
begin{center}
begin{tabular}{rrrrrrr}
hline
& 1 & 2 & 3 & 4 & 5 & 6 \
hline
1 & 181.21 & 169.01 & 130.03 & 135.93 & 142.31 & 108.11 \
2 & 106.80 & 130.71 & 186.43 & 126.46 & 167.28 & 137.91 \
3 & 162.69 & 198.98 & 188.33 & 184.30 & 147.02 & 197.38 \
4 & 132.42 & 150.50 & 148.69 & 134.31 & 129.52 & 172.72 \
hline
end{tabular}
end{center}
end{table}

! Undefined control sequence.
l.1 begin
          {table}[ht]
?
Process interrupted by user

## Standard xtable use
print(xtable(summary(npk.aov)))

% latex table generated in R 2.12.2 by xtable 1.5-6 package
% Fri Aug 12 16:00:48 2011
begin{table}[ht]
begin{center}
begin{tabular}{lrrrrr}
  hline
 & Df & Sum Sq & Mean Sq & F value & Pr($>$F) \
  hline
block       & 5 & 343.29 & 68.66 & 4.45 & 0.0159 \
  N           & 1 & 189.28 & 189.28 & 12.26 & 0.0044 \
  P           & 1 & 8.40 & 8.40 & 0.54 & 0.4749 \
  K           & 1 & 95.20 & 95.20 & 6.17 & 0.0288 \
  N:P         & 1 & 21.28 & 21.28 & 1.38 & 0.2632 \
  N:K         & 1 & 33.13 & 33.13 & 2.15 & 0.1686 \
  P:K         & 1 & 0.48 & 0.48 & 0.03 & 0.8628 \
  Residuals   & 12 & 185.29 & 15.44 &  &  \
   hline
end{tabular}
end{center}
end{table}

documentclass{article}
begin{document}
...
end{document}

% latex table generated in R 2.12.2 by xtable 1.5-6 package
% Fri Aug 12 16:29:29 2011
begin{tabular}{lrrrrr}
  hline
 & Df & Sum Sq & Mean Sq & F value & Pr($>$F) \
  hline
block       & 5 & 343.29 & 68.66 & 4.45 & 0.0159 \
  N           & 1 & 189.28 & 189.28 & 12.26 & 0.0044 \
  P           & 1 & 8.40 & 8.40 & 0.54 & 0.4749 \
  K           & 1 & 95.20 & 95.20 & 6.17 & 0.0288 \
  N:P         & 1 & 21.28 & 21.28 & 1.38 & 0.2632 \
  N:K         & 1 & 33.13 & 33.13 & 2.15 & 0.1686 \
  P:K         & 1 & 0.48 & 0.48 & 0.03 & 0.8628 \
  Residuals   & 12 & 185.29 & 15.44 &  &  \
   hline
end{tabular}

print(xtable(summary(npk.aov)),floating=FALSE,latex.environments=NULL,booktabs=TRUE)

> latex(summary(npk.aov)[[1]], cdec=c(0,2,2,2,4), na.blank=TRUE,
        booktabs=TRUE, table.env=FALSE, center="none", file="", title="")

% latex.default(summary(npk.aov)[[1]], cdec = c(0, 2, 2, 2, 4),      na.blank = TRUE, booktabs = TRUE, table.env = FALSE, center = "none",      file = "", title = "")
%
begin{tabular}{lrrrrr}
toprule
multicolumn{1}{l}{}&multicolumn{1}{c}{Df}&multicolumn{1}{c}{Sum Sq}&multicolumn{1}{c}{Mean Sq}&multicolumn{1}{c}{F value}&multicolumn{1}{c}{Pr(textgreater F)}tabularnewline
midrule
block      &$ 5$&$343.29$&$ 68.66$&$ 4.45$&$0.0159$tabularnewline
N          &$ 1$&$189.28$&$189.28$&$12.26$&$0.0044$tabularnewline
P          &$ 1$&$  8.40$&$  8.40$&$ 0.54$&$0.4749$tabularnewline
K          &$ 1$&$ 95.20$&$ 95.20$&$ 6.17$&$0.0288$tabularnewline
N:P        &$ 1$&$ 21.28$&$ 21.28$&$ 1.38$&$0.2632$tabularnewline
N:K        &$ 1$&$ 33.13$&$ 33.13$&$ 2.15$&$0.1686$tabularnewline
P:K        &$ 1$&$  0.48$&$  0.48$&$ 0.03$&$0.8628$tabularnewline
Residuals  &$12$&$185.29$&$ 15.44$&$$&$$tabularnewline
bottomrule
end{tabular}

documentclass{article}
usepackage[margin=1em,paperheight=8cm,paperwidth=12cm]{geometry}
usepackage{booktabs,lipsum}
begin{document}
<<echo=F,message=F,warning=F,comment="">>=
library(xtable)
library(stargazer)
library(kableExtra)
library(Hmisc)
data("mtcars")  # some example data
df <-mtcars[1:3, 1:6]
@

<<echo=F,results="asis">>=
print(xtable(df,caption="Example with \texttt{xtable}"),
booktabs=T, caption.placement="top")
stargazer(df, summary=F,
title="Example with \texttt{stargazer}")
kable(df, booktabs = T,
caption = "Example with  \texttt{kable}  and \texttt{kableExtra}")
latex(df, file = '', caption="Example with  \texttt{Hmisc}")
@
end{document}