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Re: st: egen rowmean, loops and if


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: egen rowmean, loops and if
Date   Wed, 6 Apr 2011 00:59:23 +0100

Here is example code for a long-winded solution:

clear
set obs 10
forval j = 1/3 {
forval i = 1/8 {
gen occ_met`j'_`i' = runiform()
}
}
ds

forval i = 1/8 {
gen mean1_`i' = 0
gen mean2_`i' = 0
gen n1_`i' = 0
gen n2_`i' = 0
qui forval j = 1/3 {
replace mean1_`i' = mean1_`i' + occ_met`j'_`i' if occ_met`j'_`i' > 0.5
replace n1_`i' = n1_`i' + (occ_met`j'_`i' > 0.5)
replace mean2_`i' = mean2_`i' + occ_met`j'_`i' if occ_met`j'_`i' <= 0.5
replace n2_`i' = n2_`i' + (occ_met`j'_`i' <= 0.5)
}
replace mean1_`i' = mean1_`i' / n1_`i'
replace mean2_`i' = mean2_`i' / n2_`i'
}


On Wed, Apr 6, 2011 at 12:37 AM, Nick Cox <njcoxstata@gmail.com> wrote:

> This would be a lot easier if you -reshape-d, even temporarily.
>
> Otherwise, with this data structure: -egen, rowmean()- is a
> non-starter here and I think you need to work at a lower level,
> building up sums and counts and deriving means.
>
> A side-detail is that -foreach- is not needed here: use -forval- instead.
>
> Nick
>
> On Tue, Apr 5, 2011 at 10:09 PM, Thomas Speidel <thomas@tmbx.com> wrote:
>> I have a wide dataset:
>>  +-------------------------------------+
>>  | id   occ_~1_1   occ_~2_1   occ_~3_1 |
>>  |-------------------------------------|
>>  |  1          4          7          . |
>>  |  2        1.5          .          . |
>>  |  3        2.3        3.3          . |
>>  |  4        3.3        2.3        3.5 |
>>  |  5        1.5          .          . |
>>  |-------------------------------------|
>>  |  6        1.5          .          . |
>>  |  7        2.3          .          . |
>>  |  8        1.5          .          . |
>>  |  9        1.5        2.3        3.3 |
>>  | 10        1.5        2.3        3.3 |
>>  +-------------------------------------+
>>
>> where   occ_~1_1 = occ_met1_1
>>        occ_~2_1 = occ_met2_1
>>        occ_~3_1 = occ_met3_1
>>
>> Of course, the data is much wider (and taller), with
>> occ_metj_i      j = 1 to <=3
>>                i = 1 to <=8
>>
>> I need to create summary measures for each i that takes the mean of the
>> three j's.  Two means are to be created: one that only evaluates values
>>>1.5, and  one that only evaluates values <=1.5:
>>
>>  +-----------------------------------------------------+
>>  | id   occ_~1_1   occ_~2_1   occ_~3_1 mean1_1 mean2_1 |
>>  |-----------------------------------------------------|
>>  |  1          4          7          .    5.50       . |
>>  |  2        1.5          .          .       .    1.50 |
>>  |  3        2.3        3.3          .    2.80       . |
>>  |  4        3.3        2.3        3.5    3.03       . |
>>  |  5        1.5          .          .       .    1.50 |
>>  |-----------------------------------------------------|
>>  |  6        1.5          .          .       .    1.50 |
>>  |  7        2.3          .          .    2.30       . |
>>  |  8        1.5          .          .       .    1.50 |
>>  |  9        1.5        2.3        3.3    2.80    1.50 |
>>  | 10        1.5        2.3        3.3    2.80    1.50 |
>>  +-----------------------------------------------------+
>>
>> The main issue is that the two commands I thought of using, egen and cond,
>> do not allow replace and egen, respectively.
>> This loop is clearly wrong, but it was an attempt at producing what I need:
>> foreach j of num 1/3    {
>>        foreach i of num 1/8    {
>>                egen mean1_`i' = rowmean(occ_met1_`i' occ_met2_`i'
>> occ_met3_`i') if (occ_met`j'_`i'>1.5)
>>                egen mean2_`i' = rowmean(occ_met1_`i' occ_met2_`i'
>> occ_met3_`i') if (occ_met`j'_`i'<=1.5)
>>                }
>>        }
>>
>

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