Wednesday, March 01, 2006

Re: st: weighted cumulative sum

bys id (year): gen exper1=pr[_n-3]/3+pr[_n-2]/2+pr[_n-1]

and you could extend this to more periods (say n>3), but you will have exper1 missing for the first n periods within each panel defined by id.

see also -tsset- and [U] 11.4.3 Time-series varlists

On 2/28/06, Arik <ericl@rocketmail.com> wrote: > Hello, > > I have a panel data of firms and the number of units > of products they sell each year. I am trying to > generate some measures of production experience. > > One measure I have simply produces a cumulative sum of > the number of products sold up to the previous year: > by id: gen experience1=sum(products[_n-1]) > > I am now trying to produce more sophisticated measures > that will discount the experience by some given rate > (by, say, dividing the experience by its age). The > idea is that last year's experience is more valuable > than the experience of the year before it and so on. > > For example, if I have the following dataset > > year 1 - 30 products > year 2 - 20 products > year 3 - 10 products > year 4 - 10 products > year 5 - 20 products > > Right now, my experience measure for year 4 is > 30+20+10=60. I am looking for a command that will give > me the following value: (30/3)+(20/2)+(10/1)=30 > > Any idea how can this be done? > > Cheers, > > Arik Lifschitz

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