An object of class "vglmff" (see vglmff-class).
The object is used by modelling functions such as vglm,
and vgam.
Details
The 2-parameter Lomax distribution is the 4-parameter
generalized beta II distribution with shape parameters $a=p=1$.
It is probably more widely known as the Pareto (II) distribution.
It is also the 3-parameter Singh-Maddala distribution
with shape parameter $a=1$, as well as the
beta distribution of the second kind with $p=1$.
More details can be found in Kleiber and Kotz (2003).
The Lomax distribution has density
$$f(y) = q / [b {1 + y/b}^{1+q}]$$
for $b > 0$, $q > 0$, $y \geq 0$.
Here, $b$ is the scale parameter scale,
and q is a shape parameter.
The cumulative distribution function is
$$F(y) = 1 - [1 + (y/b)]^{-q}.$$
The mean is
$$E(Y) = b/(q-1)$$
provided $q > 1$; these are returned as the fitted values.
References
Kleiber, C. and Kotz, S. (2003)
Statistical Size Distributions in Economics and
Actuarial Sciences,
Hoboken, NJ, USA: Wiley-Interscience.