def _ad_hoc_noise(coils, ch_type='meg'):
 v = np.empty(len(coils))
 if (ch_type == 'meg'):
  axs = np.array([_is_axial_coil(coil) for coil in coils], dtype=bool)
  v[axs] = 4e-28
  v[np.logical_not(axs)] = 2.5e-25
 else:
  v.fill(1e-12)
 cov = dict(diag=True, data=v, eig=None, eigvec=None)
 return cov

def _ad_hoc_noise ( coils , ch_type = 'meg' ) : v = np . empty ( len ( coils ) ) if ( ch_type == 'meg' ) : axs = np . array ( [ _is_axial_coil ( coil ) for coil in coils ] , dtype = bool ) v [ axs ] = 4e-28 v [ np . logical_not ( axs ) ] = 2.5e-25 else : v . fill ( 1e-12 ) cov = dict ( diag = True , data = v , eig = None , eigvec = None ) return cov
create ad-hoc noise covariance .