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" <[email protected]> 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" <[email protected]> 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 <[email protected]>
>> 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: [email protected] [mailto:owner-
>>>> [email protected]] On Behalf Of Robin Luo
>>>> Sent: Saturday, February 19, 2005 1:18 PM
>>>> To: [email protected]
>>>> 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
>>>
>>> *
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>>>
>> *
>> * For searches and help try:
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>>
>
>
> *
> * For searches and help try:
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> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
*
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