The function eigen(Sm) calculates the eigenvalues and eigenvectors of a symmetric matrix Sm. The result of this function is a list of two components named values and vectors. The assignment
ev <- eigen(Sm)
will assign this list to ev. Then ev$val is the vector of eigenvalues of Sm and ev$vec is the matrix of corresponding eigenvectors. Had we only needed the eigenvalues we could have used the assignment:
evals <- eigen(Sm)$values
evals now holds the vector of eigenvalues and the second component is discarded. If the expression
eigen(Sm)
is used by itself as a command the two components are printed, with their names, at the terminal.