description:
g=NCeval(f,subst) evaluates a polynomial f with substitutions defined in a row cell subst.
arguments:
f is an NCpoly representing a polynomial
subst is a row cell of substitutions
output:
g is NCpoly where given substitutions are done in f
possible usage:
NCeval(f,subst)
example:
>> NCeval(x^2+x*y,{{x,x+y},{y,1}})
ans = x+x^2+x*y+y+y*x+y^2
>> NCeval(x^2+x*y,{x,[1 2;3 4]})
ans = 7+y 10+2*y
15+3*y 22+4*y