fn compartment(amp: f64, decay: f64, freq: f64, t: f64) -> (f64, f64)
C · exp(−(decay + i·freq)·t) evaluated as MATLAB does it: exp of the complex exponent (−decay·t, −freq·t) is e^{re}·(cos im, sin im), then scaled by C.
C · exp(−(decay + i·freq)·t)
exp
(−decay·t, −freq·t)
e^{re}·(cos im, sin im)
C