dist                    Return the distance between two subspaces
                        spanning by column space of matrices.
lynx                    Canadian Lynx Data.
pd.boots                Select the model parameters using Fourier
                        transformation method.
sdrt                    Estimate the SDR subspaces for univariate time
                        series data.
sigma_u                 The tuning parameter for the estimation of the
                        time series central mean subspace
