def bw_normal_reference(x, kernel=kernels.Gaussian):
 C = kernel.normal_reference_constant
 A = _select_sigma(x)
 n = len(x)
 return ((C * A) * (n ** (-0.2)))

def bw_normal_reference ( x , kernel = kernels . Gaussian ) : C = kernel . normal_reference_constant A = _select_sigma ( x ) n = len ( x ) return ( ( C * A ) * ( n ** ( - 0.2 ) ) )
plug-in bandwidth with kernel specific constant based on normal reference .