Return a vector with the probabilities.
The flexit equation is published in:
Abreu-Grobois, F.A., Morales-M<U+00E9>rida, B.A., Hart, C.E., Guillon, J.-M., Godfrey, M.H.,
Navarro, E. & Girondot, M. (2020) Recent advances on the estimation of the thermal
reaction norm for sex ratios. PeerJ, 8, e8451.
$$if dose < P then (1 + (2^K1 - 1) * exp(4 * S1 * (P - x)))^(-1/K1)$$
$$if dose > P then 1-((1 + (2^K2 - 1) * exp(4 * S2 * (x - P)))^(-1/K2)$$
with:
$$S1 = S/((4/K1)*(2^(-K1))^(1/K1+1)*(2^K1-1))$$
$$S2 = S/((4/K2)*(2^(-K2))^(1/K2+1)*(2^K2-1))$$