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help for extremes
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List extreme values of a variable

        extremes numvar [other_vars] [if exp] [in range] [ , n(#) {
                 frequencies | iqr[(#)] } high low list_options ]

    by ...: may be used with extremes; see help by.


Description

    extremes lists extreme values of numvar.  If other_vars are also
    specified, these are also listed for the same observations. By default,
    the extremes are the 5 lowest and the 5 highest values of numvar. The
    option n() may be used to change 5 to any other integer. The option iqr,
    used with or without an argument, may be used to select extremes
    according to their distance from the nearer quartile.  The option
    frequencies may be used to show the frequencies of distinct extreme
    values.  Missing values are ignored.


Options

    n(#) specifies a number of values to be shown in each tail. n defaults to
        5.

    frequencies specifies that frequencies of distinct values be shown. That
        is, imagine the variable treated as discrete and shown as a
        histogram. The table shows the frequencies that would be shown as the
        n leftmost and/or the n rightmost bars of the histogram. other_vars
        may not be specified with this option.

    iqr is short-hand for iqr(1.5). See just below.

    iqr(#) specifies use of a rule based on iqr (interquartile range) for
        identifying extremes. That is, calculate

                (value - upper quartile ) / iqr

        for any values at or above the upper quartile and

                (value - lower quartile) / iqr

        for any above at or below the lower quartile.  Values will be shown
        if this ratio equals or exceeds # in absolute value. iqr(1.5)
        corresponds to a common rule for identifying individual points on box
        plots. # may be 0 or positive.

    frequencies may not be combined with iqr or iqr().

    high specifies that only high values should be shown.

    low specifies that only low values should be shown.

    list_options are options of list other than noobs and subvarname.


Examples

    . extremes price make

    . extremes price make, iqr

    . extremes price make, iqr(3)

    . bysort foreign: extremes price make, iqr


Author 

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


Acknowledgement 

    This program owes a debt to Michael N. Mitchell's hilo.  A problem posed
    by Sylvain Friederich led to tabulation by frequencies.


Also see

    On-line:  help for list, hilo (if installed), adjacent (if installed)