The function subs(e) is equivalent to eval(e).

The function subs(e,n) replaces occurences of the default variable in e with the expression n.  The default variable is determined by findsym(e,1).

For scalar o, the function subs(e,o,n) replaces occurences of o, in the expression e, with n. If n is a vector or matrix, then the operations ^, + and * (and therefore - and /) are performed element-wise.

For non-scalar o, the function subs(e,o,n), replaces each element of o with the corresponding element of n. In this case, the structure and size of o and n must be the same.  The substitution of elements occurs in series.