Display 'data.table' metadata

Convenience function for concisely summarizing some metadata of all data.tables in memory (or an optionally specified environment).

tables(mb=TRUE, order.col="NAME", width=80,
       env=parent.frame(), silent=FALSE, index=FALSE)

Arguments

mb	logical; TRUE adds the rough size of each data.table in megabytes to the output under column MB.
order.col	Column name (character) by which to sort the output.
width	integer; number of characters beyond which the output for each of the columns COLS, KEY, and INDICES are truncated.
env	An environment, typically the .GlobalEnv by default, see Details.
silent	logical; should the output be printed?
index	logical; if TRUE, the column INDICES is added to indicate the indices assorted with each object, see indices.

Details

Usually tables() is executed at the prompt, where parent.frame() returns .GlobalEnv. tables() may also be useful inside functions where parent.frame() is the local scope of the function; in such a scenario, simply set it to .GlobalEnv to get the same behaviour as at prompt.

Note that on older versions of R, object.size may be slow, so setting mb=FALSE may speed up execution of tables significantly.

Setting silent=TRUE prints nothing; the metadata are returned as a data.table, invisibly, whether silent is TRUE or FALSE.

Value

A data.table containing the information printed.

See also

data.table, setkey, ls, objects, object.size

Examples

DT = data.table(A=1:10, B=letters[1:10])
DT2 = data.table(A=1:10000, ColB=10000:1)
setkey(DT,B)
tables()
#>    NAME   NROW NCOL MB   COLS KEY
#> 1:   DT     10    2  0    A,B   B
#> 2:  DT2 10,000    2  0 A,ColB    
#> Total: 0MB