Re: st: forvalues loop doesn't work?

[Nick Cox <njcoxstata@gmail.com>]

econqian222 is confusing the -if- command and the -if- qualifier. See

FAQ     . . . . . . . . . . . . . . . . . . . . .  if command vs. if qualifier
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  J. Wernow
        6/00    I have an if command in my program that only seems
                to evaluate the first observation, what's going on?
                http://www.stata.com/support/faqs/lang/ifqualifier.html

In brief, the command

if index == `i'

will always be interpreted as

if index[1] == `i'

which will be true just once. When that happens, the loop will be executed.

Nick

On Mon, May 7, 2012 at 10:52 AM, Ronnie Babigumira <rb.glists@gmail.com> wrote:

> Looks like the problem is that the -replace- is not conditional so that last r(p90) replaces all
>
> Does this do what you want?
>
> qui sum index
> forvalues i=1/`r(max)'{
> sum quantity if index == `i', detail
> replace q_cutoff90=r(p90) if index == `i'
> }


On Monday, May 7, 2012 at 11:42 AM, econqian222 wrote:

>> I have tried to record percentile 90 of quantity for each value of
>> index, unfortunately, my result still only record the percentile 90 of
>> quantity for all the values of index, so what's the problem of my program?
>> My program goes like the following:
>>
>> forvalues i=1/4760{
>> if index==`i' {
>> sum quantity, detail
>> replace q_cutoff90=r(p90)
>> }
>> }
>>
>> My data goes as this:
>> index quantity q_cutoff90
>> 1 4 .
>> 1 67 .
>> 2 89 .
>> 2 57 .
>> 2 91 .
>> 3 98 .
>> 3 95 .
>> 3 27 .
>> . . .
>> . . .
>> 4760 88 .
>> 4760 56 .
>>
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