Am 08.11.2018 um 10:46 schrieb oleg_komashko@ukr.net:

> it is the angle of the root

The matter is in that it is a

function of the angle

I have failed to guess what

the function it is. That's why

I have asked.

I'm not sure I understand the question. If the root is 0.5 + i*0.1, then the angle should be atan(0.1 / 0.5) = 0.19739556 (in radians).
Then you still have to factor in that the ARMA "roots" that are given are probably not the ones inside the unit circle (for stability), but in fact the inverse roots outside the circle. So before taking the atan you'd have to invert the root.

Is that what you mean?
thanks,
sven