autocov function
Implementation
List<double> autocov(List<double> x, int maxLag) {
final m = mean(x);
final n = x.length;
final ac = List<double>.filled(maxLag+1, 0.0);
for (int k=0; k<=maxLag; k++) {
double s = 0.0;
for (int t=k; t<n; t++) s += (x[t]-m) * (x[t-k]-m);
ac[k] = s / n;
}
return ac;
}