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help for xtab                                             (author:  Tony Brady)
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Tabulate longitudinal data

        xtab varname [, i(varname) t(varname) missing occasion(ever | never |
                 first | last | _N | # ) ]

by ... : may be used with the above command; see help by.


Description

If you have not read help for xt, please do so now.

xtab, a generalization of tabulate, performs one-way tabulations of
cross-sectional time-series (xt) data. It is more flexible than xttab, allowing
several choices of the occasion within cluster to tabulate.


Options

i(varname) specifies the variable name corresponding to i; see help xt.

t(varname) specifies the variable name corresponding to t; see help xt.

missing requests that missing values be treated like other values in
    calculations of counts and percentages.

occasion(occ) determines which observations within cluster i are to be used in
    the tabulation. occ must be one of:

        ever          means clusters are characterised by values appearing in
                      any valid observation within the cluster; the default.
        never         tabulates the number of clusters that do not contain the
                      value in any valid observation.
    (*) first or 1    uses the first valid observation to characterise
                      clusters.
    (*) last or _N    uses the last valid observation to characterise clusters.
    (*) #             requests the observation on occasion # within each
                      cluster to be used in the tabulation.

Unstarred occasions do not require the time variable t to be defined whereas
starred occasions do.


Examples

        . xtab beta, i(idnum)
        . xtab beta, i(idnum) t(date) occ(last) miss

        . iis idnum
        . tis date
        . xtab beta, occ(2)

        . bysort region: xtab aspirin, occ(never)


Author

        Tony Brady, Sealed Envelope Ltd, U.K.
        tony@sealedenvelope.com


Also see

 Manual:  [R] xt
On-line:  help for xt, xttab, xtdes, xtsum