Link function applied to the association parameter
$\alpha$, which is real.
See Links for more choices.
earg
List. Extra argument for the link.
See earg in Links for general information.
iapar
Numeric. Optional initial value for $\alpha$.
By default, an initial value is chosen internally.
If a convergence failure occurs try assigning a different value.
Assigning a value will override the argument method.init.
method.init
An integer with value 1 or 2 which
specifies the initialization method. If failure to converge occurs
try the other value, or else specify a value for ia.
Value
An object of class "vglmff" (see vglmff-class).
The object is used by modelling functions such as vglm
and vgam.
Details
The cumulative distribution function is
$$P(Y_1 \leq y_1, Y_2 \leq y_2) = y_1 y_2
( 1 + \alpha (1 - y_1) (1 - y_2) )$$
for real $\alpha$
(the range is data-dependent).
The support of the function is the unit square.
The marginal distributions are the standard uniform distributions.
When $\alpha = 0$ then the random variables are
independent.
A variant of Newton-Raphson is used, which only seems to work for an
intercept model.
It is a very good idea to set trace=TRUE.
This VGAM family function is prone to numerical difficulties.
References
Castillo, E., Hadi, A. S., Balakrishnan, N. Sarabia, J. S. (2005)
Extreme Value and Related Models with Applications in Engineering and Science,
Hoboken, N.J.: Wiley-Interscience.