st: RE: RE: carryforward

[Nick Cox <n.j.cox@durham.ac.uk>]

If this method is one of imputing missing values that in practice will be varying by a constant that was the last observed value, then as Tony implies it clearly can be problematic. 

But the method of replacing missing values by previous non-missing values is one I often use with small datasets entered by hand. When the observations come in blocks, I only need to type in values for the first identifier in each block, and then -replace- appropriately. 

Sometimes datasets arrive like that too. Only the first value in a block of some blocked variable is explicit, so you have to fill in (or fill out) implied similar values.  

Nick 
n.j.cox@durham.ac.uk 

Lachenbruch, Peter

This method has been seriously questioned and gives very poor answers generally.  A true p-value may be reported anywhere from 0.01 to0.15 when it should be 0.05.  I strongly urge it not be used.

________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] On Behalf Of David Kantor [kantor.d@att.net]

Once again, thanks to Kit Baum, a new version of -carryforward- is
available on SSC.
This upgrade adds the -if- and -in- qualifiers.
Actually, the upgrade was written a long time ago, but never got
uploaded until now. Sorry, if that was my fault.

-carryforward- carries values from one observation to the next,
filling in missing values.

-ssc install carryforward-

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/