Display 'data.table' metadata

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

Usage

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

Arguments

mb

a function which accepts a data.table and returns its size in bytes. By default, type_size (same as TRUE) provides a fast lower bound by excluding the size of character strings in R's global cache (which may be shared) and excluding the size of list column items (which also may be shared). A column "MB" is included in the output unless FALSE or NULL.

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.

mb = utils::object.size provides a higher and more accurate estimate of size, but may take longer. Its default units="b" is appropriate.

Setting silent=TRUE prints nothing; the metadata is 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 10000    2  0 A,ColB [NULL]
#> Total: 0MB using type_size