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From |
Ichiro Fujikake <fujikake@cc.miyazaki-u.ac.jp> |

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

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

Date |
Mon, 21 Feb 2005 09:28:45 +0900 |

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/

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

**References**:**Re: st: RE: question about calculating discounted sum***From:*Robin Luo <rluosf@gmail.com>

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