ELEMENTS

ELEMENTS(x;e1;e2) forms a sub-structure of x. If x is a vector or a diagonal matrix, then only e1 should be specified; this then indicates the selected elements of x. If x is a rectangular matrix, then both e1 and e2 should be given, to specify respectively the selected rows and columns of x. For a symmetric matrix x, if the same rows and columns are to be selected (giving a symmetric matrix) then only e1 should be specified; otherwise both e1 and e2 should be given (and the result is a matrix).