help for ^qweibull4^

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

^qweibull4^ varname [^if^ exp] [^in^ range] [ ^,^ ^b(^#^)^ ^c(^#^)^ ^gr^id graph_options ]

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

^qweibull4^ plots the quantiles of varname against the quantiles of a two-parameter Weibull distribution with scale parameter b and shape parameter c. By default, b and c are taken from S_2 and S_3, which is where ^wbull^ puts maximum likelihood estimates of them.

The probability density function is

c c - 1 c f(x) = - (x / b) exp(- (x / b) ) b

for x >= 0, b > 0 and c > 0.

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

Options -------

^b(^#^)^ sets b to #.

^c(^#^)^ sets c to #.

^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 --------

. ^wbull precip^ . ^qweibull4 precip^

Author ------

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

Also see --------

On-line: help for @graph@, @wbull@, @pweibull4@