data.table Printing Options

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.

# S3 method for 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
    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.
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 codedata.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).

See also

print.default

Examples

  #output compression
  DT <- data.table(a = 1:1000)
  print(DT, nrows = 100, topn = 4)
#>          a
#>    1:    1
#>    2:    2
#>    3:    3
#>    4:    4
#>   ---     
#>  997:  997
#>  998:  998
#>  999:  999
#> 1000: 1000

  #`quote` can be used to identify whitespace
  DT <- data.table(blanks = c(" 12", " 34"),
                   noblanks = c("12", "34"))
  print(DT, quote = TRUE)
#>    "blanks" "noblanks"
#> 1:    " 12"       "12"
#> 2:    " 34"       "34"

  #`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)
#>        a      b          c
#>    <int> <cplx>     <IDat>
#> 1:     0   0+0i 2016-02-01
#> 2:     0   0+0i 2016-02-02
#> 3:     0   0+0i 2016-02-03

  #`row.names` can be eliminated to save space
  DT <- data.table(a = 1:3)
  print(DT, row.names = FALSE)
#>  a
#>  1
#>  2
#>  3

  #`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)
#> Key: <b, a>
#> Indices: <a__b>, <a>
#>    a b c
#> 1: 1 4 7
#> 2: 2 5 8
#> 3: 3 6 9