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From |
Xixi Lin <winnielxx@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

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

Date |
Mon, 11 Feb 2013 11:40:55 -0500 |

Hi Maarten, Yes, it works. Thanks. Best, Xixi Lin On Mon, Feb 11, 2013 at 11:25 AM, Maarten Buis <maartenlbuis@gmail.com> wrote: > Did you actually try what Nick proposed? If you did than you would > have seen that what you said is not true. If you drop the observation > (row) "id 1, period 1" than the observation (row) "id 1, period 2" > will still be there. > > *------------------ begin example ------------------ > drop _all > input 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 > end > > drop if missing(x1, x2) > > list > *------------------- end example ------------------- > (For more on examples I sent to the Statalist see: > http://www.maartenbuis.nl/example_faq ) > > Hope this helps, > Maarten > > On Mon, Feb 11, 2013 at 5:16 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/ >> * >> * 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/ > > > > -- > --------------------------------- > Maarten L. Buis > WZB > Reichpietschufer 50 > 10785 Berlin > Germany > > http://www.maartenbuis.nl > --------------------------------- > * > * 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/ * * 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/

**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>

**Re: st: How to drop missing values by period?***From:*Maarten Buis <maartenlbuis@gmail.com>

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