I am using IC cadence 6.1.3. I need to use this expression

L = imag(Z_{11} - Z_{12}Z_{21}/Z_{22})
/ (2*pi*f)

to find the inductor's self resoance frequency. However, after I run sp analysis, the "zp" I obtained from direct plot separate the real and imaginary part. I need to obtain a complex representation of impedance z from the simulation result, so I can fit it into the equation above. I tried to use zp(1 1 ?result "sp") in the output setup expression, but apparently it doesn't give me the correct answer. If someone know my question and can give me an answer, in IC cadence 6.1.3 after sp analysis, how could I find the complex representation of impedance Z (Z11 Z22 Z12 Z21) that I can used in calculator to find self resonant frequency of inductor. And how do I represent the complex expressoin of S11 S22 as well? Please help if you know the answer. Thank you!