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From |
Friedrich Huebler <huebler@rocketmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: Re: Collapse & Missing Values |

Date |
Wed, 28 Sep 2005 14:05:26 -0700 (PDT) |

Eric, Here is one way to preserve the missing value. . bysort date: egen sum = sum(amount) . replace sum = . if amount==. (2 real changes made, 2 to missing) . bysort date: keep if _n==1 (3 observations deleted) . drop amount . rename sum amount . clist, noobs date amount 10-Oct-1990 189 11-Oct-1990 . 12-Oct-1990 107 Friedrich Huebler --- "Eric G. Wruck" <ewruck@econalytics.com> wrote: > I just learned, rather inconveniently, that collapse doesn't work > the > way I'd like when encountering missing values. Here's an example: > . l > > +----------------------+ > | date amount | > |----------------------| > 1. | 10-Oct-1990 200 | > 2. | 10-Oct-1990 -75 | > 3. | 10-Oct-1990 64 | > 4. | 11-Oct-1990 . | > 5. | 12-Oct-1990 107 | > |----------------------| > 6. | 12-Oct-1990 . | > +----------------------+ > > . collapse (sum) net_amt=amount, by(date) > > . l > > +-----------------------+ > | date net_amt | > |-----------------------| > 1. | 10-Oct-1990 189 | > 2. | 11-Oct-1990 0 | > 3. | 12-Oct-1990 107 | > +-----------------------+ > > . > The problem is for the single 11-Oct-1990 observation. After > collapsing, the missing value becomes a zero; in this instance I > would have preferred it remain missing. The 12-Oct-1990 treatment > is > fine & what I expected. I suppose I could delete observations > before > performing the collapse but it would be better if there was some > other option. Is there? > > > Grazie, > > > Eric > > -- > > =================================================== > > Eric G. Wruck > Econalytics > 2535 Sherwood Road > Columbus, OH 43209 > > ph: 614.231.5034 > cell: 614.330.8846 > eFax: 614.573.6639 > eMail: ewruck@econalytics.com > website: http://www.econalytics.com > > ==================================================== __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Collapse & Missing Values***From:*"Eric G. Wruck" <ewruck@econalytics.com>

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