R: Display 'data.table' metadata

tables {data.table} | R Documentation

## Display 'data.table' metadata

### Description

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

### Usage

    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()

[Package data.table version 1.11.8 Index]