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Re: st: How to Calculate A Variable of Maximum Values up to each of the 114 periods in my sample?


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: How to Calculate A Variable of Maximum Values up to each of the 114 periods in my sample?
Date   Fri, 14 Dec 2012 17:19:57 +0000

Getting the maximum so far is an FAQ on the Stata website. See also a function in -egenmore- (SSC).

Nick

On 14 Dec 2012, at 16:53, Yuval Arbel <yuval.arbel@gmail.com> wrote:

Dear Statalisters,

I am trying to generate a variable, which will give me the maximum
value of another variable (reduct_per) up to each of the 114 periods
in my sample.

Note that the function -max- works only with -egen-, namely it creates
a constant maximum, and not a running maximum..

I therefore wrote the following set of commands:

by appt: egen y=max(reduct_per)
by appt: gen max=reduct_per if time_index==0
by appt: replace max=reduct_per if reduct_per==y
by appt: replace max=reduct_per[_n-1] if reduct_per<=reduct_per[_n-1]
& max==. & time_index==1
by appt: replace max=reduct_per if max==. & time_index==1

by appt: replace max=max[_n-1] if reduct_per<=max[_n-1] & max==. &
time_index==2
by appt: replace max=reduct_per if max==. & time_index==2

by appt: replace max=max[_n-1] if reduct_per<=max[_n-1] & max==. &
time_index==3
by appt: replace max=reduct_per if max==. & time_index==3

by appt: replace max=max[_n-1] if reduct_per<=max[_n-1] & max==. &
time_index==4
by appt: replace max=reduct_per if max==. & time_index==4

by appt: replace max=max[_n-1] if reduct_per<=max[_n-1] & max==. &
time_index==5
by appt: replace max=reduct_per if max==. & time_index==5

by appt: replace max=max[_n-1] if reduct_per<=max[_n-1] & max==. &
time_index==6
by appt: replace max=reduct_per if max==. & time_index==6

and so on. My question is whether there is a more elegant way to
generate this variable. More specifically I would like to know
whether I need to write a loop, and if so how would I write it so that
I don't have to repeat the last two commands for 114
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