Lines Matching refs:SDcols

31   .SDcols,
117         When \code{j} is a character vector of column names, a numeric vector of column positions to select or of the form \code{startcol:endcol}, and the value returned is always a \code{data.table}. \code{with=FALSE} is not necessary anymore to select columns dynamically. Note that \code{x[, cols]} is equivalent to \code{x[, ..cols]} and to \code{x[, cols, with=FALSE]} and to \code{x[, .SD, .SDcols=cols]}.}
144     \item{.SDcols}{ Specifies the columns of \code{x} to be included in the special symbol \code{\link{.SD}} which stands for \code{Subset of data.table}. May be character column names or numeric positions. This is useful for speed when applying a function through a subset of (possible very many) columns; e.g., \code{DT[, lapply(.SD, sum), by="x,y", .SDcols=301:350]}.
146     For convenient interactive use, the form \code{startcol:endcol} is also allowed (as in \code{by}), e.g., \code{DT[, lapply(.SD, sum), by=x:y, .SDcols=a:f]}.
148     Inversion (column dropping instead of keeping) can be accomplished be prepending the argument with \code{!} or \code{-} (there's no difference between these), e.g. \code{.SDcols = !c('x', 'y')}.
150     Finally, you can filter columns to include in \code{.SD} based on their \emph{names} according to regular expressions via \code{.SDcols=patterns(regex1, regex2, ...)}. The included columns will be the \emph{intersection} of the columns identified by each pattern; pattern unions can easily be specified with \code{|} in a regex. You can filter columns on \code{values}  by passing a function, e.g. \code{.SDcols=\link{is.numeric}}. You can also invert a pattern as usual with \code{.SDcols=!patterns(...)} or \code{.SDcols=!is.numeric}.
277 DT[, ..colNum]                 # same, equivalent to DT[, .SD, .SDcols=colNum]
369 DT[, .SD, .SDcols=x:y]                  # select columns 'x' through 'y'
370 DT[ , .SD, .SDcols = !x:y]              # drop columns 'x' through 'y'
371 DT[ , .SD, .SDcols = patterns('^[xv]')] # select columns matching '^x' or '^v'
423 # using rleid, get max(y) and min of all cols in .SDcols for each consecutive run of 'v'
424 DT[, c(.(y=max(y)), lapply(.SD, min)), by=rleid(v), .SDcols=v:b]