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help for sdline
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SD line (reduced major axis)

        sdline yvar xvar [if exp] [in range] [ , generate(ysdlvar) nograph
                 graph_options ]


Description

    sdline produces a scatter plot of yvar versus xvar with the SD line or
    reduced major axis superimposed.

    This line goes through the intersection of the means (mean of xvar, mean
    of yvar) and has slope

        sign of corr(xvar, yvar) * (SD of yvar) / (SD of xvar)


Options

    generate() saves the values of yvar predicted from the SD line as a new
        variable.

    graph_options are options allowed with twoway scatter.  The default
        options include ms(oh none) connect(none l) sort.  Know that the data
        points are plotted first and the SD line second by twoway scatter.
        These options include plot_option (Stata 8 only) and addplot_option
        (Stata 9).

    nograph suppresses the graph and is for situations in which only the
        numerical results for the SD line are desired.


Examples

    . sdline length width
    . sdline length width, gen(length_sd)
    . sdline length width, addplot(lfit length width)


Saved results 

    r(N)            number of observations
    r(ymean)        mean of yvar
    r(ysd)          SD of yvar
    r(xmean)        mean of xvar
    r(xsd)          SD of xvar
    r(slope)        slope of SD line


Author

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


Acknowledgements

    Allan Reese found typos in this help.


Also see

    On-line: twoway scatter