Question

I’m sure this is very simple, but I ask Mathematica for the characteristic polynomial of an equation, as follows:

m={
 {0, n, 0, c1},
 {R, 0, 4, c2},
 {0, R, 0, 0},
 {0, 0, R, c4}
}
CharacteristicPolynomial[m,x]

Now, I would like to save the returned polynomial as a function, so I can later call it (presumably with something like f[1]). Alas, I’ve been unable to figure out how to do this.

Answer 1

This is fairly straightforward. Simply do this

f[x_] = CharacteristicPolynomial[m,x]

Note the use of Set (=) not SetDelayed (:=) which forces CharacteristicPolynomial to be evaluated once. If you used SetDelayed, then it would be evaluated every time f is evaluated.