{smcl}
{.-}
help for {cmd:harmby} {right:(Roger Newson)}
{.-}


{title:Harmonize values of variables within by-groups}

{p 8 27}
{cmd:harmby} {it:varlist} [ , {cmd:by(}{it:by_varlist}{cmd:)} ]


{title:Description}

{p}
{cmd:harmby} ("{it:harm}onize within {it:by}-groups") checks that each variable in the {it:varlist}
has no more than one value, other than the standard missing value, in each of the by-groups specified
by {cmd:by()}, or in the whole data set, if {cmd:by()} is not specified. A standard missing value is {hi:.}
for a numeric variable, or the empty string {hi:""} for a string variable. If this condition is true,
then {cmd:harmby} replaces all standard missing values in the by-group (or data set) by the one value
that is not standard missing, if such a value exists,
and takes no action if all values in a by-group (or data set) are standard missing.
{cmd:harmby} is useful if there are variables whose values should be unique within each by-group
(or within the data set), and new observations with standard missing values for these variables
have been added to some or all of the by-groups by {help merge},
or by {help ingap}, which is downloadable from {help ssc:SSC}.


{title:Options}

{p 0 4}{cmd:by(}{it:by_varlist}{cmd:)} specifies a list of variables defining the by-groups.
The data set does not have to be sorted by those variables, and remains sorted in its
original order after {cmd:harmby} has run.


{title:Examples}

{p 8 16}{inp:. harmby N N_clust depvar, by(idnum idstr)}{p_end}


{title:Author}

{p}
Roger Newson, King's College, London, UK.
Email: {browse "mailto:roger.newson@kcl.ac.uk":roger.newson@kcl.ac.uk}


{title:Also see}

{p 0 21}
{bind: }Manual:  {hi:[R] merge}, {hi:[R] by}
{p_end}
{p 0 21}
On-line:  help for {help merge}, {help by}
{p_end}
{p 10 21}
help for {help ingap} if installed
{p_end}