get => _tf ?? new TransferFunction(_b.Take(_numeratorSize).ToArray(), _a.Take(_denominatorSize).ToArray());
get => _tf ?? new TransferFunction(_b.Take(_kernelSize).ToDoubles());
get => _tf ?? new TransferFunction(_b.Take(_kernelSize).ToArray());
// created lazily or set specifically if needed get => _tf ?? new TransferFunction(_b.Take(_numeratorSize).ToDoubles(), _a.ToDoubles());