{smcl}
{* 12Jun2006}{...}
{cmd:help groupdata}
{hline}

{title:Title}

{p 4 8 2}
{bf: groupdata -- Prepares data for grouped conditional logit regression}

{title:Syntax}

{p 8 17 2}
{cmd:groupdata}
{varlist} 
{cmd:,} 
{bind: {cmdab:d:ep:}({depvar}) {cmdab:gr:oupid:}(groupid) {cmdab:ch:oiceid:}(choiceid)}

where:
{it:groupid} is a unique group identifier
{it:choiceid} is a unique choice identifier

{title:Description}

{p 4 4 2}
{cmd:groupdata} converts the data set in memory to a new data set that can be used
with commands that deal with multinomial type data such as grouped conditional
logit {helpb multin} and dirichlet-multinomial regression {helpb dirmul}. 
The dataset in memory must be in the format required by the command {helpb clogit}.
Suppose you have a data set in the format required by clogit:

y  x1  x2 gid cid
0   0   4   1   1
0   1   4   1   2
1   1   6   1   3
1   2   2   2   1
0   1   4   2   2
0   3   5   2   3
0   0   4   3   1
1   1   4   3   2
0   1   6   3   3
0   2   6   4   1
1   3   7   4   2
0   2   5   4   3
0   1   5   4   4
1   2   2   5   1
0   1   4   5   2
0   3   5   5   3

After issuing the command

{p 4 8 2}{cmd:. groupdata x1 x2, dep(y) groupid(gid) choiceid(cid)}

your data will look like

x1  x2  gid cid y
0   4   1   1   0
1   4   1   2   1
1   6   1   3   1
2   2   2   1   2
1   4   2   2   0
3   5   2   3   0
2   6   4   1   0
3   7   4   2   1
2   5   4   3   0
1   5   4   4   0

{title:Examples}

{p 4 8 2}{cmd:. groupdata age gender, dep(y) gr(id) ch(choice)}

{title:Author}

Paulo Guimaraes, Division of Research, University of South Carolina.
Email: {browse "mailto:guimaraes@moore.sc.edu":guimaraes@moore.sc.edu} 

{title:Also See}

{p 4 13 2}
{helpb multin}
{helpb dirmul}