Subset a trajectory flow, preserving the contract

Filters the trajectories of a flow object while keeping it a valid flow: $tree and absorbed_into are reattached by transitive bypass (a kept child points to its nearest kept ancestor; NA if none survives) and $docs_per_group follows the kept nodes. The result is a view, not a census: the call is recorded in attr(, "pruned") and shown by print(). Dispatches for any detector whose result inherits from birddog_flow (the contract class), so future detection methods are subsettable for free.

Usage

# S3 method for class 'birddog_flow'
subset(x, subset, target = NULL, ...)

Arguments

x

A birddog_flow object (or a subclass from a future detector).

subset

Logical expression on the columns of x$trajectories, e.g. size >= 50 or type == "central".

target

Optional character vector of traj_ids: keep each target and its whole tributary subtree (the watershed). Intersects with subset.

...

Ignored (base generic compatibility).

Value

An object of the same class as x, passing validate_flow().

See also

sniff_trajectory_braid(), validate_flow()

Other trajectory detection: is_flow(), sniff_trajectory_braid(), sniff_trajectory_channel(), sniff_trajectory_dag(), validate_flow()