In SPL, the matrix exists as a second-order sequence, such as [[22,7.25],[38,71.2833],[26,7.925],[35,53.1],[35,8.05]], each of the subsequencerepresents a row, usually a sample record; Members at the same position ofeverysubsequence represent a column, such as [22,38,26,35,35] as the first column of the matrix, usually a variable.