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

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

Subject |
st: RE: RE: RE: listing all observations of particular id's |

Date |
Sun, 29 Aug 2010 19:34:14 +0100 |

It's like this. 1. by A: egen other_anyB1 = max(B) Stata sees the -by- first, and asks: Are observations -sort-ed by A? If the answer is No, an error is generated. 1'. bysort A: egen other_anyB1 = max(B) Stata sees the -by- first, and asks: Are observations -sort-ed by A? If the answer is No, the -sort-ing is done, and no error is generated. Stata proceeds to the -egen- call. 2. egen anyB1 = max(B), by(A) This is in fact an old syntax which is no longer documented, but I remember it and still use it. There are some further subtleties: * -by()- isn't even an undocumented option of -egen-. It _may be_ an undocumented function of whatever -egen- function is being called. . viewsource _gmax.ado shows that -by()- is allowed as an option in this case, which is why it works. And the -sort-ing is done for you within the _gmax program. * As -egen- is -sortpreserve, you get your old -sort- order back. So any changes in -sort- order done by -egen, max()- are undone. Note: When you call -egen-'s <foobar> function, Stata needs to find an _g<foobar> program on your -adopath-. Nick n.j.cox@durham.ac.uk Martin Weiss On the occasion of this thread and NJC`s solution: Why is it that Stata requires no -sort-ing in Nick`s solution, but does require it if I prefix the -by-? (For -max-, -sort-ing should not matter...) *********** clear* inp byte(A B) 1 0 1 1 2 0 1 0 2 1 3 0 2 0 3 0 2 1 end egen anyB1 = max(B) , by(A) by A: egen other_anyB1 = max(B) *********** Nick Cox This is an FAQ. An answer is egen anyB1 = max(B) , by(id) l if anyB1 The rationale is discussed at tedious length in How do I create a variable recording whether any members of a group (or all members of a group) possess some characteristic? <http://www.stata.com/support/faqs/data/anyall.html> Nick n.j.cox@durham.ac.uk Abhimanyu Arora The basic simplified problem is as follows. 2 variables A (id) and B(0/1) I would like to list all observations of all A's for which there is at least one B=1. -list- lists only the particular observations... * * 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: listing all observations of particular id's***From:*Abhimanyu Arora <abhimanyu.arora1987@gmail.com>

**st: RE: listing all observations of particular id's***From:*Nick Cox <n.j.cox@durham.ac.uk>

**st: RE: RE: listing all observations of particular id's***From:*"Martin Weiss" <martin.weiss1@gmx.de>

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