Link function applied to the association parameter
$\alpha$, which is real
and $-1 < \alpha < 1$.
See Links for more choices.
ialpha
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 imethod.
imethod
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 ialpha.
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 $-1 < \alpha < 1$.
The support of the function is the unit square.
The marginal distributions are the standard uniform distributions.
When $\alpha = 0$ the random variables are
independent.
References
Balakrishnan, N. and Lai, C.-D. (2009)
Continuous Bivariate Distributions,
2nd ed.
New York: Springer.