st: RE: AW: Creating index relative to other observations

["Frederick Guy" <f.guy@bbk.ac.uk>]

Thanks, I guess I was unclear on this aspect of the problem. For each observation, the sum I'm talking about is of measurements made relative to all other observations (or more generally, to some set of other observations) in the sample.

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Martin Weiss
Sent: 29 April 2010 19:09
To: statalist@hsphsun2.harvard.edu
Subject: st: AW: Creating index relative to other observations


<> 

".. sum up the results of these computations,".


Creating sums can mean different things in Stata. It may sound trite, but
the easiest is simply to -generate- a sum by adding values with a "+" sign.
If you want the total of a variable, look at -egen, total()-. If you want a
running sum, take a look at -help sum()-.



HTH
Martin

-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Frederick Guy
Gesendet: Donnerstag, 29. April 2010 19:52
An: statalist@hsphsun2.harvard.edu
Betreff: st: Creating index relative to other observations

I have need to use information from all observations (about 1800 of
them) to create a new variable.

The variable created is a weighted sum of the inverse of geographical
distances between observation i and all j n.e. i. I have longitude and
latitude for each observation, and computation of the distance from any
i to any j is straightforward. What I don't know is how to get Stata to
loop over all observation and sum up the results.

For every observation i, I think I need to

(a) loop through all j n.e. I, doing computations involving variables
x1, x2(i) and x1, x2(j), and then

(b) sum up the results of these computations, returning a value which
becomes variable x3 for that i.

I expect there's a straightforward way to do this. Any suggestions?


Frederick Guy
Senior Lecturer
Department of Management
School of Business, Economics, and Infomatics
Birkbeck College, University of London
Malet St
London WC1E 7HX



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