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Re: st: Mean calculation under consideration of different dates


From   shausen@smail.uni-koeln.de
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Mean calculation under consideration of different dates
Date   Fri, 14 Jan 2011 19:14:24 +0100

Again - thank you very much Nick for your excellent advice. My Stata formula now looks like this
gen meanb= .
quietly forval i=1/`=_N'{
summarize forecast if ticker==ticker[`i'] & fpedats==fpedats[`i']
& inrange(estdats[`i'] - estdats, 1, 90), meanonly
replace meanb= r(mean) in `i'
}

and it works perfectly. One last question: is there a possibility that the mean is only calculated if there are at least two prior forecasts that also meet the inrange restriction? Right now Stata also calcultaes means that only consist of one forecast.


Zitat von Nick Cox <njcoxstata@gmail.com>:

This is discussed explicitly in the Tip earlier cited with code examples.

As you say, you need to add a condition of the form

id == id[`i']

to the -if- condition. Here -id- is an example identifier which tells
you what group you are in. Your variable name may well be different.

Using more words, you are insisting that

identifier == identifier of this observation

or that the observations used must be in the same group.

Nick

On Wed, Jan 12, 2011 at 1:24 PM,  <shausen@smail.uni-koeln.de> wrote:

first many thanks to Nick for sending me the Stata Journal Tip. Nevertheless
I still got some problems with telling Stata to calculate the mean for the
whole dataset but apply the loop for different groups defined by two
variables (company ticker and a date). Based on the tip I tried:

gen meanb= .
quietly forval i=1`/=_N'{
summarize forecast if inrange (estdats[`i']-estdats,1,90), meanonly
replace meanb= r(mean) in `i'
}

How can I tell Stata to differ between certain groups? Using bysort before
the loop does not work but I guess I should include some "sort-command"
within the loop anyway. Maybe a tag() or id=id[`i']? Any advice is
appreciated.



Zitat von Nick Cox <njcoxstata@gmail.com>:

Check out

SJ-7-3  pr0033  . . . . . . . . . . . . . .  Stata tip 51: Events in
intervals
       . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J.
Cox
       Q3/07   SJ 7(3):440--443                                 (no
commands)
       tip for counting or summarizing irregularly spaced
       events in intervals

<http://www.stata-journal.com/sjpdf.html?articlenum=pr0033>

On Thu, Jan 6, 2011 at 6:43 PM,  <shausen@smail.uni-koeln.de> wrote:

I've got a large dataset that includes forecasts of growth rates for
different periods reported by different analysts at different dates. I
already sorted the data to make sure that the analysts forecasts refer to
the same firm and the same date.
In anext step the mean of the analysts growth rate forecasts should be
calculated under the assumption that only those forecasts should be taken
into account that were issued maximum 90 days prior to the forecast of a
certain analyst.
analyst   est date    forecast   mean
11       15.Feb 2010    0,3      0,225
22       08.Jan 2010    0,2      0,3
33       01.Jan 2010    0,25
44       01.Nov 2009    0,35

The mean calculation for analyst 11 for example consists of the forecasts
of
analyst 22 and analyst 33 to be in line with the maximum 90 days
assumption.
In addition the analysts own forecast should not be considered when
calculating the mean but I guess Stata does it automatically.
Any hints or tips are warmly welcomed.

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