Set the significant digits for each column in a xtable for fancy Sweave output

This tip may be useful in the situations when you need to set the number of digits to print for the different columns in a matrix/data.frame to be outputted as a LaTeX table.
 For example:

#install.packages("xtable")
#library(xtable)
tmp <- matrix(rnorm(9), 3, 3)
xtmp <- xtable(tmp)
digits(xtmp) <- c(0,0,3,4)
print(xtmp, include.rownames = FALSE) # row names suppressed

See here for a nice gallery depicting a large variety of outputs you can produce using the xtable package.