R: data.table Printing Options

print.data.table {data.table}

R Documentation

data.table Printing Options

Description

print.data.table extends the functionalities of print.data.frame.

Key enhancements include automatic output compression of many observations and concise column-wise class summary.

Usage

  ## S3 method for class 'data.table'
print(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, ...)

Arguments

`x`	A `data.table`.
`topn`	The number of rows to be printed from the beginning and end of tables with more than `nrows` rows.
`nrows`	The number of rows which will be printed before truncation is enforced.
`class`	If `TRUE`, the resulting output will include above each column its storage class (or a self-evident abbreviation thereof).
`row.names`	If `TRUE`, row indices will be printed alongside `x`.
`col.names`	One of three flavours for controlling the display of column names in output. `"auto"` includes column names above the data, as well as below the table if `nrow(x) > 20`. `"top"` excludes this lower register when applicable, and `"none"` suppresses column names altogether (as well as column classes if `class = TRUE`.
`print.keys`	If `TRUE`, any `key` and/or `index` currently assigned to `x` will be printed prior to the preview of the data.
`trunc.cols`	If `TRUE`, only the columns that can be printed in the console without wrapping the columns to new lines will be printed (similar to `tibbles`).
`quote`	If `TRUE`, all output will appear in quotes, as in `print.default`.
`timezone`	If `TRUE`, time columns of class POSIXct or POSIXlt will be printed with their timezones (if attribute is available).
`...`	Other arguments ultimately passed to `format`.

Details

By default, with an eye to the typically large number of observations in a data.table, only the beginning and end of the object are displayed (specifically, head(x, topn) and tail(x, topn) are displayed unless nrow(x) < nrows, in which case all rows will print).

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)