Valve seats wear out in certain diesel engines, each with 16 valve seats.
The dataset served as an example of recurrence data in Nelson (1995),
which consists of valve-seat replacements on 41 engines in a fleet.
The covariates are named
ID, Days, and No., where
ID: The engine number;Days: Engine age in days;No.: Event indicator, '1' for a valve-seat replacement and, '0' for the censoring age of an engine.