st: data management problem

[Kit Baum <baum@bc.edu>]

sacrificial lamb

With regard to Wanli Zhao's problem of counting the number of  
products per firm, using his original data:

list
tabstat firm, by(firm) stat(N)
reshape wide product, i(firm) j(dept) string
ds prod*
local allprod `r(varlist)'
g allprod=""
foreach v of local allprod {
	qui replace allprod = allprod + `v' + " "
}

g uniqprod=""
g nprod=.
su firm,mean
forv i=1/`r(N)' {
	local prodlist = allprod[`i']
	local prodlist : subinstr local prodlist "," "",all
	local uniqprod : list uniq prodlist
	qui replace uniqprod = "`uniqprod'" in `i'
	local nprod : word count `uniqprod'
	qui replace nprod = `nprod' in `i'
}

list firm uniqprod nprod

     +--------------------------+
     | firm    uniqprod   nprod |
     |--------------------------|
  1. |    1   a b c r d       5 |
  2. |    2   d f I y g       5 |
     +--------------------------+




Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html


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