Given $\beta \in \R , \theta \in \R ^d$ the
logistic model (the
logistic probabilistic
model) corresponding to the parameters
$\beta $ and $\theta $ is the function $p: X
\to [0, 1]$ defined by
\[
p(x) = \frac{1}{1 + \exp(-\theta ^\top x - \beta )}
\]