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help for circqvm
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Quantile-quantile plot for von Mises distribution fitted to circular data

        circqvm varname [if exp] [in range] [, show(numlist) plot(plot)
                 scatter_options]


Description

    circqvm gives a quantile-quantile plot for the fit of a von Mises (a.k.a.
    circular normal) distribution to a circular variable on a scale between 0
    and 360 degrees. circvm is used to fit the distribution, estimating the
    two parameters vector mean mu and concentration parameter kappa. Both
    observed and expected quantiles are rotated so that each set is centred
    on the observed vector mean.  Each is nevertheless labelled in terms of
    varname.

    This plot was suggested by Fisher (1993). However, he uses a sine((angle
    - centre) / 2) scale, which has the merit of pulling in the tails and
    stretching the region near the centre of the distribution, but the
    disadvantage, as with any transformation, of being one step further away
    from the data.


Options

    show() specifies a numlist of axis labels to be shown, overriding the
        default.

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

    scatter_options are any options allowed with scatter.


Examples

    . circqvm wallasp
 
    . circqvm wallasp, show(0(45)315)


References

    Fisher, N.I. 1993. Statistical analysis of circular data.  Cambridge:
        Cambridge University Press.


Author

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


Also see

    On-line: help for circvm, circpvm