nsdiffs function
Implementation
int nsdiffs(List<double> x, int s, {int maxD = 1}) {
if (maxD == 0 || s <= 1) return 0;
final r = kpss(x);
if (!r.stat.isNaN && r.stat > 0.739) {
final y = differenceSeas(x, s, 1);
final r2 = kpss(y);
if (!r2.stat.isNaN && r2.stat <= 0.739) return 1;
}
return 0;
}