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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: How to drop missing values by period? |

Date |
Mon, 11 Feb 2013 16:22:12 +0000 |

Sorry, but this looks to me like the same question, and my answer is the same. Please do try my code, or the equivalent, on a copy of your data. Note that you don't -drop- in terms of identifier or period. Nick On Mon, Feb 11, 2013 at 4:16 PM, Xixi Lin <winnielxx@gmail.com> wrote: > Hi Nick, > > I know what do you mean, if I, for instance, drop id 1, then in period > 2, id 1 is also gone. I am thinking is that possible only to drop id 1 > in period 1, while in other periods, id 1 is still there. I am not > sure did I clearify this time? > > Best, > Xixi Lin > > On Mon, Feb 11, 2013 at 10:25 AM, Nick Cox <njcoxstata@gmail.com> wrote: >> Thanks for the example. Stata usually takes care of this for you in that >> >> 1. A command uses as many as observations as possible. >> >> 2. Most statistical commands ignore missing values. >> >> But in your example >> >> . drop if missing(x1, x2) >> >> will drop observations if either -x1- or -x2- is missing. It's not >> clear to me that you need to think of this period by period, as that >> makes no difference to the outcome. >> >> Nick >> >> On Mon, Feb 11, 2013 at 3:18 PM, Xixi Lin <winnielxx@gmail.com> wrote: >>> Hi Nick, >>> >>> Thanks for the instant reply. What I mean is like: >>> id period x1 x2 >>> 1 1 1 4 >>> 2 1 2 . >>> 3 1 . 2 >>> 1 2 4 4 >>> 2 2 5 3 >>> 3 2 . 2 >>> >>> In period 1, I want to keep id 1 because id 2 and id 3 have missing >>> values; in period 2, I want to keep id 1 &2, because id 3 has missing >>> values. >>> >>> I have time series data, but I wanna do a cross-sectional regressions >>> and wanna keep the maximum of observations. So I am wondering if it is >>> possible to drop obs only in one period while keeping it in another >>> period. >>> >>> Thanks. >>> Xixi Lin >>> >>> On Mon, Feb 11, 2013 at 9:59 AM, Nick Cox <njcoxstata@gmail.com> wrote: >>>> This sounds to me as if you want -keep- and -drop- the same >>>> observations. That can't be done. >>>> >>>> Perhaps you should show what your data look like with variable names, >>>> and link your question to such an example. >>>> >>>> Nick >>>> >>>> On Mon, Feb 11, 2013 at 2:53 PM, Xixi Lin <winnielxx@gmail.com> wrote: >>>> >>>>> I tried to drop missing values period by period, in 120 periods. In other >>>>> words, in period 1, I want to drop the observations if dependent variables >>>>> have missing values only in period 1; while in period 2, drop the >>>>> observations if dependent variables have missing values only in period 2, >>>>> should keep those that missing in period 1 but not missing in period 2. For >>>>> instance: >>>>> >>>>> In period 1, I want to keep id 1; in period 2, I want to keep id 1 &2. >>>>> >>>>> Does anyone knows how to do that? Thanks a lot. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: How to drop missing values by period?***From:*Xixi Lin <winnielxx@gmail.com>

**References**:**st: How to drop missing values by period?***From:*Xixi Lin <winnielxx@gmail.com>

**Re: st: How to drop missing values by period?***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: How to drop missing values by period?***From:*Xixi Lin <winnielxx@gmail.com>

**Re: st: How to drop missing values by period?***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: How to drop missing values by period?***From:*Xixi Lin <winnielxx@gmail.com>

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