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From |
"David Radwin" <dradwin@mprinc.com> |

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

Subject |
st: RE: Easy Question? Counting cases based on a "target" case |

Date |
Wed, 26 Dec 2012 10:24:58 -0800 (PST) |

Ben, I don't think you need to loop over observations, but you can loop over values which is fairly efficient. Something like this: levelsof price, local(prices) foreach p of local prices { gen near`p' = inrange(price, `=`p'-2000', `=`p'+2000') } egen countnear = rowtotal(near*) In the example above I use all prices, but you could substitute the following line for the first and second line above: foreach p of numlist 1900 2500 4000 6500 10000 { David -- David Radwin Senior Research Associate MPR Associates, Inc. 2150 Shattuck Ave., Suite 800 Berkeley, CA 94704 Phone: 510-849-4942 Fax: 510-849-0794 www.mprinc.com > -----Original Message----- > From: owner-statalist@hsphsun2.harvard.edu [mailto:owner- > statalist@hsphsun2.harvard.edu] On Behalf Of Ben Hoen > Sent: Wednesday, December 26, 2012 10:06 AM > To: statalist@hsphsun2.harvard.edu > Subject: st: Easy Question? Counting cases based on a "target" case > > I want to perform a function that I think would be easy but I can't wrap > my > head around how to perform it without looping through each case. > > I want to create a count of the number of records in the file that meet a > certain criteria based on a respective case's value. So for example using > the auto dataset: > > *====================begin > sysuse auto, clear > g id=_n > egen nearprice2000=count(id) if... //count the number of other cases in > the > dataset if the price of the car is within $2000 of the price of this > cases' > (i.e., target) car's price > > *====================end > > The egen command is how I thought I would resolve this, but I can't figure > it out exactly. The nearprice2000 would equal the count for each case of > the number of other cases in the dataset that have a price that is either > +/- $2000 from the particular case's price. So if the full dataset had > only > 5 prices: 1900, 2500, 4000, 6500, and 10000, their respective nearprice200 > values would be: 2, 3, 2, 2, and 1 (if itself would be included in the > count) or 1, 2, 1, 1, and 0 (if itself would NOT be included in the count) > > I might be able to do this by looping through the cases, but I know that > is > not encouraged by other more experienced users. > > Any advice would be greatly appreciated. > > Ben * * 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**:**st: RE: RE: Easy Question? Counting cases based on a "target" case***From:*"Ben Hoen" <bhoen@lbl.gov>

**References**:**st: Easy Question? Counting cases based on a "target" case***From:*"Ben Hoen" <bhoen@lbl.gov>

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