relation_at_lag()

double MayaFlux::Kinesis::relation_at_lag ( std::span< const double >  a, std::span< const double >  b, long  lag  )

inlinenoexcept

Correlation between two spans at a single fixed lag.

Parameters

a	First span
b	Second span
lag	Samples to offset b relative to a; positive tests whether b's later samples resemble a's earlier ones

Returns

Correlation over the overlapping region at that lag, or zero if the overlap is too short to be meaningful

The bounded, single-lag counterpart to Discrete::cross_correlate; see this file's header comment for the relationship. Exists as its own function, distinct from relation_lag below, because a caller who already knows the lag they care about (a fixed device latency, a known frame offset between two sensors) should not pay for a search over a range to confirm what they already know.

Definition at line 111 of file Relation.hpp.

{
    const auto na = static_cast<long>(a.size());
    const auto nb = static_cast<long>(b.size());
 
    const long start_a = std::max(0L, -lag);
    const long start_b = std::max(0L, lag);
    const long overlap = std::min(na - start_a, nb - start_b);
 
    if (overlap < 2)
        return 0.0;
 
    return correlation(
        a.subspan(static_cast<size_t>(start_a), static_cast<size_t>(overlap)),
        b.subspan(static_cast<size_t>(start_b), static_cast<size_t>(overlap)));
}

References a, b, and correlation().

Referenced by relation_lag().

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