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From |
Robin Luo <rluosf@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: question about calculating discounted sum |

Date |
Sun, 20 Feb 2005 22:36:34 -0800 |

Ichiro, It works perfect. Thank you so much! Robin On Mon, 21 Feb 2005 09:33:22 +0900, Ichiro Fujikake <fujikake@cc.miyazaki-u.ac.jp> wrote: > I am sorry. There was a typo. I meant > > sort firmid year > by firmid: gen i=_n > qui sum i > local imax=r(max) > gen sum=income > forv j=1/`imax' { > local h= `j'-1 > forv k=1/`h' { > by firmid: replace sum=sum+income[_n-`k']/(`k'+1) if i==`j' > } > } > > Ichiro > > On 05.2.21 9:28, "Ichiro Fujikake" <fujikake@cc.miyazaki-u.ac.jp> wrote: > > > Hi Robin > > > > I hope the following codes help you. > > > > sort firmid year > > by firmid: gen i=_n > > qui sum i > > local imax=r(max) > > gen sum=income > > forv j=1/`imax' { > > local h= `j'-1 > > forv k=1/`j-1' { > > by firmid: replace sum=sum+income[_n-`k']/(`k'+1) if i==`j' > > } > > } > > > > Ichiro > > > > > > On 05.2.21 8:36, "Robin Luo" <rluosf@gmail.com> wrote: > > > >> Btw, Scott, concerning `=seq', do you have any idea about how to > >> integrate a variable into "forvalue" loop? > >> > >> Many thanks! > >> > >> Robin > >> > >> > >> On Sun, 20 Feb 2005 16:37:04 -0600, Scott Merryman <smerryman@kc.rr.com> > >> wrote: > >>> How about attacking this problem directly: > >>> > >>> bysort firm (year): gen num = _n > >>> gen sum = 0 > >>> by firm: replace sum = income + income[1]/num[2] if num== 2 > >>> by firm: replace sum = income + income[1]/num[3] + income[2]/num[2] /// > >>> if num == 3 > >>> by firm: replace sum = income + income[1]/num[4] + income[2]/num[3] + /// > >>> income[3]/num[2] if num == 4 > >>> by firm: replace sum = income + income[1]/num[5] + income[2]/num[4] + /// > >>> income[3]/num[3] + income[4]/num[2] if num == 5 > >>> by firm: replace sum = income + income[1]/num[6] + income[2]/num[5] + /// > >>> income[3]/num[4] + income[4]/num[3] + income[5]/num[2] if num == 6 > >>> > >>> Hope this helps, > >>> > >>> Scott > >>> > >>> P.S. `=seq' is the same as seq[1] or 1 > >>> > >>>> -----Original Message----- > >>>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner- > >>>> statalist@hsphsun2.harvard.edu] On Behalf Of Robin Luo > >>>> Sent: Saturday, February 19, 2005 1:18 PM > >>>> To: statalist@hsphsun2.harvard.edu > >>>> Subject: st: question about calculating discounted sum > >>>> > >>>> I need to calculate discounted sum for a variable in a panel data. My > >>>> data is like: > >>>> > >>>> FirmID year income > >>>> 100 1980 50000 > >>>> 100 1981 51000 > >>>> 100 1982 54000 > >>>> 100 1983 60000 > >>>> 100 1984 59000 > >>>> 100 1985 62000 > >>>> 101 1970 18000 > >>>> 101 1971 18500 > >>>> 101 1972 20000 > >>>> 101 1973 24000 > >>>> > >>>> Basically, the data is a panel data, grouped by "FirmID", with > >>>> hundreds of frims. What I need to do is to calculate a moving > >>>> discounted sum of income for each firm-year. That is, calculate a sum > >>>> of income from a firm's first year to the current year, but each > >>>> year's income will be discounted by that year's distance to the > >>>> current year and the discount rate is the inverse of the distance > >>>> "1/(current year - year +1)". For example, for firm 100 at 1982, this > >>>> calculation would be like: 54000 + 51000*1/2 +50000*1/3, while for > >>>> firm 100 at 1984 it would be like 59000 + 60000*1/2 + 54000*1/3 + > >>>> 51000*1/4 + 50000*1/5. I tried the following program: > >>>> > >>>> by FirmID: gen seq=_n > >>>> > >>>> gen suminc=0 > >>>> > >>>> quietly forval i=1/`=seq' { > >>>> by FirmID: replace suminc = suminc + income[`i']/(`=seq' - `i' > >>>> +1) > >>>> } > >>>> > >>>> But problems are: 1) the loop seems not allowing "by" command; 2) the > >>>> loop does not really launch, because even after I get rid of "by > >>>> FirmID" the loop seems to go only one cycle instead of "_n" cycles. > >>>> > >>>> Many many thanks for any help! > >>>> > >>>> Robin Luo > >>> > >>> * > >>> * 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/ > >>> > >> * > >> * 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/ > >> > > > > > > * > > * 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/ > > > > * > * 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/ > * * 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**:**Re: st: RE: question about calculating discounted sum***From:*Ichiro Fujikake <fujikake@cc.miyazaki-u.ac.jp>

**Re: st: RE: question about calculating discounted sum***From:*Ichiro Fujikake <fujikake@cc.miyazaki-u.ac.jp>

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