check_feature_na        Find features with (specified amount of)
                        missingness
check_row_na            Find number of and which rows contain any
                        missingness
feature_cor             High dimensional imputation via batch processed
                        chained random forests Build correlation matrix
flatten_mat             Flatten and arrange cor matrix to be df
hdImpute                Complete hdImpute process: correlation matrix,
                        flatten, rank, create batches, impute, join
impute_batches          Impute batches and return completed data frame
mad                     Compute variable-wise mean absolute differences
                        (MAD) between original and imputed dataframes.
