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help for pbeta
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Probability plot for data versus fitted beta distribution

pbeta varname [if exp] [in range] [weight] [, grid param(# #)
show(condition) generate(newvar1 newvar2)
graph_options ]

where graph_options are

rlopts(cline_options) plot(plot) scatter_options twoway_options

fweights and aweights are allowed; see help weights.

Description

pbeta produces a probability plot for varname compared with a
two-parameter beta distribution with probability density function for
variable 1 > x > 0, shape parameters a > 0 and b > 0 of [1 / B(a, b) ] x
^(a - 1) (1 -x)^ (b - 1).  Here B(,) is the beta function.  By default,
maximum likelihood estimation is carried out, using betafit, which should
be installed separately.

Remarks

In the majority of cases, pbeta will be used to fit an beta distribution
on the fly and to assess that fit. In some cases, it may be of interest
to compare data with a beta distribution with known or hypothesised
parameters, which may be specified using the param() option. In all cases
it is important not only to specify any if or in restrictions, but also
to specify relevant weights, which will (unless constant) affect the
configuration of the plot.

Options

grid is equivalent to yla(0(.25)1, grid) xla(0(.25)1, grid).

param() may be used to supply parameter values (namely, shape parameters)
directly for use in estimation of fitted quantiles.  a and b should
be provided as separate values in precisely that order.

show() may be used to specify that you wish to restrict the graph
according to some condition, say looking at one tail of the
distribution only. Note that if and in should not be used for this
purpose.

generate() specifies the names of two new variables, the first to hold
beta probabilities and the second to hold empirical probabilities.

graph_options are rlopts(cline_options), plot(plot), scatter_options, and
twoway_options.

rlopts(cline_options) affect the rendition of the reference line; see
help cline_options.

plot(plot) provides a way to add other plots to the generated graph; see
help plot_option.

scatter_options affect the rendition of the plotted points; see help
scatter.

twoway_options are any of the options documented in help twoway_options
excluding by().  These include options for titling the graph (see
help title_options) and options for saving the graph to disk (see
help saving_option).

Examples

. pbeta hail

. pbeta hail, gen(hail_bet hail_emp)

Author

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

References

Evans, M., Hastings, N. and Peacock, B. 2000. Statistical distributions.
New York: John Wiley.

Johnson, N.L., Kotz, S. and Balakrishnan, N. 1995.  Continuous univariate
distributions: Volume 2. New York: John Wiley.

Also see

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