Is the distribution parameter object consistent with the corresponding distribution? The distribution functions (cdfgam, pdfgam, quagam, and
lmomgam) require consistent parameters to return the cumulative
probability (nonexceedance), density, quantile, and L-moments of the distribution,
respectively. These functions internally use the are.pargam.valid
function. The parameters are restricted to the following conditions.
$$\alpha > 0 \mbox{ and } \beta > 0\mbox{.}$$
Alternatively, a three-parameter version is available following the parameterization of the Generalized Gamma distribution used in the gamlss.dist package and and for lmomco is documented under pdfgam. The parameters for this version are
$$\mu > 0;\;\; \sigma > 0;\;\; -\infty < \nu < \infty$$
for parameters number 1, 2, 3, respectively.