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New generics is_discrete() and is_continous() with methods for all distribution objects
in the package. The is_discrete() methods return TRUE for every distribution that is discrete
on the entire support and FALSE otherwise. Analogously, is_continuous() returns TRUE for
every distribution that is continuous on the entire support and FALSE otherwise. Thus, for
mixed discrete-continuous distributions both methods should yield FALSE (#90).
New logical argument elementwise = NULL in apply_dpqr() and hence inherited in cdf(), pdf(), log_pdf(), and quantile(). It provides type-safety when
applying one of the functions to a vector of distributions d to a numeric
argument x where both d and x are of length n > 1. By setting elementwise = TRUE
the function is applied element-by-element, also yielding a vector of length n.
By setting elementwise = FALSE the function is applied for all combinations
yielding an n-by-n matrix. The default elementwise = NULL corresponds to FALSE
if d and x are of different lengths and TRUE if the are of the same length
n > 1 (#87).
Extended support for various count data distributions, now enompassing both the Poisson
and negative binomial distributions along with various adjustments for zero counts
(hurdle, inflation, and truncation, respectively). More details are provided in the
following items (#86).
New d/p/q/r functions for hnbinom, zinbinom, ztnbinom, and ztpois similar
to the corresponding nbinom and pois functions from base R.
New HurdleNegativeBinomial(), ZINegativeBinomial(), ZTNegativeBinomial(), and ZTPoisson() distribution constructors along with the corresponding S3 methods for the
"usual" generics (except skewness() and kurtosis()).
New prodist() methods for extracting the fitted/predicted probability distributions from
models estimated by hurdle(), zeroinfl(), and zerotrunc() objects from either the pscl package or the countreg package.
Added argument prodist(..., sigma = "ML") to the lm method for extracting the
fitted/predicted probability distribution from a linear regression model. In the previous
version the prodist() method always used the least-squares estimate of the error variance
(= residual sum of squares divided by the residual degrees of freedom, n - k), as also
reported by the summary() method. Now the default is to use the maximum-likelihood estimate
instead (divided by the number of observations, n) which is consistent with the logLik()
method. The previous behavior can be obtained by specifying sigma = "OLS" (#91).
Similarly to the lm method the glm method prodist(..., dispersion = NULL) now, by
default, uses the dispersion estimate that matches the logLik() output. This is based
on the deviance divided by the number of observations, n. Alternatively, dispersion = "Chisquared" uses the estimate employed in the summary() method,
based on the Chi-squared statistic divided by the residual degrees of freedom, n - k.
Small improvements in methods for various distribution objects: Added support() method
for GEV-based distributions (GEV(), GP(), Gumbel(), Frechet()). Added a random() method for the Tukey() distribution (using the inversion method).