# block trace command

Syntax

block trace keyword

Primary keywords:

Trace an object. The positions and velocities of certain objects can be sampled and stored during a model run with this command. The resulting path through space can be plotted. Only one object may be traced per block trace command. Traces may be added at any time. The contents of all traces can be erased with the purge keyword, and all traces can be deleted with the delete keyword. A summary of all traces can be obtained by using the LIST trace command.

Each trace is given a unique ID number, based on the order in which the TRACE commands are issued. However, a specific ID number can be assigned with the id keyword. All traces are sampled at a single sampling interval. By default, the sampling interval for the trace mechanism is 10 steps. The sampling interval can be changed with the trace rep keyword or the SET trace rep command. Different trace intervals cannot be assigned to different traces.

id i

Trace the position and velocity of a block centroid with ID i.

name s

Assign a name to the trace.

position v

Trace the position and velocity of a block with a centroid closest to v.