help for ^qgamma4^

Quantile-quantile plot for data vs fitted gamma distribution ------------------------------------------------------------

^qgamma4^ varname [^if^ exp] [^in^ range] [ ^,^ ^a^lpha^(^#^)^ ^b^eta^(^#^)^ ^t^ransform ^gr^id graph_options ]

Description -----------

^qgamma4^ plots the quantiles of varname against the quantiles of a two-parameter gamma distribution with shape parameter alpha and scale parameter beta. By default, alpha and beta are taken from S_alpha and S_beta, which is where ^gamma4^ puts maximum likelihood estimates of them.

Note: this is the original version of ^qgamma^, written for Stata 4. Users of Stata 8 up should switch to ^qgamma^.

Options -------

^alpha(^#^)^ sets alpha to #.

^beta(^#^)^ sets beta to #.

^transform^ applies a cube-root transform to both data and fitted quantiles. This may be useful for highly skewed data. The result should be closer to a Gaussian (normal) distribution.

^grid^ adds grid lines at the .05, .10, .25, .50, .75, .90, and .95 quantiles.

graph_options are any of the options allowed with ^graph, twoway^; see help for ^graph^.

Examples --------

. ^gamma4 precip^ . ^qgamma4 precip^ . ^qgamma4 precip, t^

Author ------

Nicholas J. Cox, University of Durham, U.K. n.j.cox@@durham.ac.uk

Also see --------

On-line: help for @graph@, @gamma4@, @pgamma4@