Test if argument is a vector
isvec(v) isvec(v,l)
ISVEC(V) is true (1) if the argument V is a 3-vector, else false (0).
ISVEC(V, L) is true (1) if the argument V is a vector of length L, either a row- or column-vector. Otherwise false (0).
differs from Scilab builtin function ISVECTOR, the latter returns true for the case of a scalar, ISVEC does not.