If location or scale are omitted, they assume the
default values of 0 and 1 respectively.
The Logistic distribution with location \(= \mu\) and
scale \(= \sigma\) has distribution function
$$
F(x) = \frac{1}{1 + e^{-(x-\mu)/\sigma}}%
$$
and density
$$
f(x)= \frac{1}{\sigma}\frac{e^{(x-\mu)/\sigma}}{(1 + e^{(x-\mu)/\sigma})^2}%
$$
The generation algorithm uses inversion. The parameters
lb and ub can be used to generate variates from
the Logistic distribution truncated to the interval (lb,ub).