# compute body/local command

## Syntax

``` LAMMPS
compute ID group-ID body/local input1 input2 ...
```

-   ID, group-ID are documented in [compute](compute) command

-   body/local = style name of this compute command

-   one or more keywords may be appended

-   keyword = *id* or *type* or *integer*

        *id* = atom ID of the body particle
        *type* = atom type of the body particle
        *integer* = 1,2,3,etc = index of fields defined by body style

## Examples

``` LAMMPS
compute 1 all body/local type 1 2 3
compute 1 all body/local 3 6
```

## Description

Define a computation that calculates properties of individual body
sub-particles. The number of data generated, aggregated across all
processors, equals the number of body sub-particles plus the number of
non-body particles in the system, modified by the group parameter as
explained below. See the [Howto body](Howto_body) page for more details
on using body particles.

The local data stored by this command is generated by looping over all
the atoms. An atom will only be included if it is in the group. If the
atom is a body particle, then its $N$ sub-particles will be looped over,
and it will contribute $N$ data to the count of data. If it is not a
body particle, it will contribute 1 datum.

For both body particles and non-body particles, the *id* keyword will
store the ID of the particle.

For both body particles and non-body particles, the *type* keyword will
store the type of the particle.

The *integer* keywords mean different things for body and non-body
particles. If the atom is not a body particle, only its *x*, *y*, *z*
coordinates can be referenced, using the *integer* keywords 1,2,3. Note
that this means that if you want to access more fields than this for
body particles, then you cannot include non-body particles in the group.

For a body particle, the *integer* keywords refer to fields calculated
by the body style for each sub-particle. The body style, as specified by
the [atom_style body](atom_style), determines how many fields exist and
what they are. See the [Howto_body](Howto_body) doc page for details of
the different styles.

Here is an example of how to output body information using the [dump
local](dump) command with this compute. If fields 1, 2, and 3 for the
body sub-particles are (*x*, *y*, *z*) coordinates, then the dump file
will be formatted similar to the output of a [dump atom or custom](dump)
command.

``` LAMMPS
compute 1 all body/local type 1 2 3
dump 1 all local 1000 tmp.dump index c_1[1] c_1[2] c_1[3] c_1[4]
```

## Output info

This compute calculates a local vector or local array depending on the
number of keywords. The length of the vector or number of rows in the
array is the number of data as described above. If a single keyword is
specified, a local vector is produced. If two or more keywords are
specified, a local array is produced where the number of columns = the
number of keywords. The vector or array can be accessed by any command
that uses local values from a compute as input. See the [Howto
output](Howto_output) page for an overview of LAMMPS output options.

The [units](units) for output values depend on the body style.

## Restrictions

> none

## Related commands

[dump local](dump)

## Default

none