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Autocorrelation zero lag normalized · case 02

Sample count replaces zero-lag energy normalization.

Member previewVariant 2 · 3 implementations · 4 checks per implementation

Case contract

Integer sample values and compatible sample-array lengths. Rational results are reduced Fraction strings; spacing is positive unless explicitly stated otherwise. 0<=lag<=len(values); use the uncentered lagged product sum divided by full-signal energy. A zero-energy signal returns None. Exact operational definition: str(Fraction(sum(a*b for a,b in zip(values,values[lag:])),sum(v*v for v in values))) if any(values) else None

Why this case matters

Small exact fixtures expose this error without platform timing, external services, or probabilistic observations. Discrete calculus results depend on the stated convention.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
fixture 1: ([1, 2, 3], 1)	`"8/3"`	`"4/7"`	Failed

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