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\name{print.data.table}
\alias{print.data.table}
\title{ data.table Printing Options }
\description{
\code{print.data.table} extends the functionalities of \code{print.data.frame}.
Key enhancements include automatic output compression of many observations and concise column-wise \code{class} summary.
}
\usage{
\method{print}{data.table}(x,
topn=getOption("datatable.print.topn"), # default: 5
nrows=getOption("datatable.print.nrows"), # default: 100
class=getOption("datatable.print.class"), # default: FALSE
row.names=getOption("datatable.print.rownames"), # default: TRUE
col.names=getOption("datatable.print.colnames"), # default: "auto"
print.keys=getOption("datatable.print.keys"), # default: FALSE
trunc.cols=getOption("datatable.print.trunc.cols"), # default: FALSE
quote=FALSE,
timezone=FALSE, \dots)
}
\arguments{
\item{x}{ A \code{data.table}. }
\item{topn}{ The number of rows to be printed from the beginning and end of tables with more than \code{nrows} rows. }
\item{nrows}{ The number of rows which will be printed before truncation is enforced. }
\item{class}{ If \code{TRUE}, the resulting output will include above each column its storage class (or a self-evident abbreviation thereof). }
\item{row.names}{ If \code{TRUE}, row indices will be printed alongside \code{x}. }
\item{col.names}{ One of three flavours for controlling the display of column names in output. \code{"auto"} includes column names above the data, as well as below the table if \code{nrow(x) > 20}. \code{"top"} excludes this lower register when applicable, and \code{"none"} suppresses column names altogether (as well as column classes if \code{class = TRUE}. }
\item{print.keys}{ If \code{TRUE}, any \code{\link{key}} and/or \code{\link[=indices]{index}} currently assigned to \code{x} will be printed prior to the preview of the data. }
\item{trunc.cols}{ If \code{TRUE}, only the columns that can be printed in the console without wrapping the columns to new lines will be printed (similar to \code{tibbles}). }
\item{quote}{ If \code{TRUE}, all output will appear in quotes, as in \code{print.default}. }
\item{timezone}{ If \code{TRUE}, time columns of class POSIXct or POSIXlt will be printed with their timezones (if attribute is available). }
\item{\dots}{ Other arguments ultimately passed to \code{format}. }
}
\details{
By default, with an eye to the typically large number of observations in a \code{data.table}, only the beginning and end of the object are displayed (specifically, \code{head(x, topn)} and \code{tail(x, topn)} are displayed unless \code{nrow(x) < nrows}, in which case all rows will print).
}
\seealso{\code{\link{print.default}}}
\examples{
#output compression
DT <- data.table(a = 1:1000)
print(DT, nrows = 100, topn = 4)
#`quote` can be used to identify whitespace
DT <- data.table(blanks = c(" 12", " 34"),
noblanks = c("12", "34"))
print(DT, quote = TRUE)
#`class` provides handy column type summaries at a glance
DT <- data.table(a = vector("integer", 3),
b = vector("complex", 3),
c = as.IDate(paste0("2016-02-0", 1:3)))
print(DT, class = TRUE)
#`row.names` can be eliminated to save space
DT <- data.table(a = 1:3)
print(DT, row.names = FALSE)
#`print.keys` can alert which columns are currently keys
DT <- data.table(a=1:3, b=4:6, c=7:9, key="b,a")
setindexv(DT, c("a", "b"))
setindexv(DT, "a")
print(DT, print.keys=TRUE)
# `trunc.cols` will make it so only columns that fit in console will be printed
# with a message that states the variables not shown
old_width = options("width" = 40)
DT <- data.table(thing_11 = vector("integer", 3),
thing_21 = vector("complex", 3),
thing_31 = as.IDate(paste0("2016-02-0", 1:3)),
thing_41 = "aasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf",
thing_51 = vector("integer", 3),
thing_61 = vector("complex", 3))
print(DT, trunc.cols=TRUE)
options(old_width)
}
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