Indexing functions have the following signature:
function(x, ...). x denotes a signal-values vector (see
tbl_mbte for details). In other words, the measured values of
a signal get passed as a numeric vector. The job of an indexing function is
to find the start- and end-indices of a subsignal (used by
mbte_extract_subsignals).
A list with the following names should be returned:
Start indices of the found subsignals.
End indices of the found subsignals.
The length of the returned indices must match the number of found subsignals (e.g. 3 Subsignals found ==> length of start- and end-indices vectors must equal 3). The indices-vectors have to be of type integer.