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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: Re: AW: drop command & missing values |

Date |
Mon, 12 Oct 2009 13:20:06 +0100 |

Unless memory is limited, you can avoid confusions like this by not using -drop- at all. Just let Stata determine what to omit. Nick n.j.cox@durham.ac.uk Francesco Trivieri thank you very much. I eventually understood the problem. It was depending on the lagged dependent variable. If I do 1) drop if x>123 rather than 2) drop if x>123 & x!=. I am eliminating observations that Stata may use to calculate Y-1. So, I avoid the problem by using 2). From: "Martin Weiss" <martin.weiss1@gmx.de> > Well, in the absence of an example that is reproducible to all it is > difficult to diagnose the problem. In my example, both approaches end up > delivering the same nobs... > > > ************* > use http://www.stata-press.com/data/r7/abdata.dta, clear > > replace w=. in 200/250 > > preserve > drop if w>3.4 > xtabond2 n w k, iv(w k, eq(level)) small h(1) > restore > > preserve > drop if w>3.4 & w!=. > xtabond2 n w k, iv(w k, eq(level)) small h(1) > restore > ************* > Francesco Trivieri > thank you very much for your answers. I am always including the x variable > in my estimation, I don't understand why: > > drop if x>123 > xtabond2 Y Y_1 X Z .... > the estimation sample is 8100 > > drop if x>123 & x!=. > xtabond2 Y Y_1 X Z .... > the estimation sample is 12200 * * 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/

**References**:**st: drop command & missing values***From:*"Francesco Trivieri" <francesco.trivieri@unical.it>

**st: AW: drop command & missing values***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**st: Re: AW: drop command & missing values***From:*"Francesco Trivieri" <francesco.trivieri@unical.it>

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