st: re: purging a dataset

[Kit Baum <baum@bc.edu>]

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To follow up on Philippe's suggestion

sysuse auto, clear
reg trunk rep78
gen sample=e(sample)
pwcorr price trunk if sample

You can use the qualifier 'if sample' on each command to restrict it to use the regression sample. Another approach is to do

sysuse auto, clear
reg trunk rep78
gen sample=e(sample)
preserve
drop if !sample
pwcorr price trunk 
...
...
restore

all commands given after the 'drop if !sample' will be performed only on the estimation sample. Any variables created between 'preserve' and 'restore' will be dropped when you restore. Sometimes it is useful to work (temporarily) with this subset dataset.

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


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