poly (Symbolic Math Toolbox)

Characteristic polynomial of a matrix

Syntax

```
p = poly(A)
p = poly(A, v)
```

Description

If A is a numeric array, poly(A) returns the coefficients of the characteristic polynomial of A. If A is symbolic, poly(A) returns the characteristic polynomial of A in terms of the default variable x. The variable v can be specified in the second input argument.

Note that if A is numeric, poly(sym(A)) approximately equals poly2sym(poly(A)). The approximation is due to roundoff error.

Examples

The statements

syms z
A = gallery(3) 
p = poly(A)
q = poly(sym(A))
s = poly(sym(A),z)

return

A = 
  -149   -50  -154
   537   180   546
   -27    -9   -25

p = 
1.0000   -6.0000   11.0000   -6.0000

q=
x^3-6*x^2+11*x-6

s =
z^3-6*z^2+11*z-6

See Also

poly2sym, jordan, eig, solve

numden poly2sym