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Re: st: Looping over variables


From   Ingeborg Forthun <ingeborg.forthun@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Looping over variables
Date   Wed, 19 Dec 2012 14:43:29 +0100

Ok, no problem. Thank you very much for your help!

Ingeborg

2012/12/19 Nick Cox <njcoxstata@gmail.com>:
> Your results are correct. The problem was mine; precedence rules mean
> that the code should have been
>
> replace n_preg = n_preg + (inlist(aa`j', 1, 5) | (inlist(aa`j', 2, 3,
> 4, 6, 7) & inrange(aa`J', 13, .)))
>
> to ensure that the entire logical condition is evaluated separately.
> Sorry about that.
>
> Nick
>
> On Wed, Dec 19, 2012 at 12:30 PM, Ingeborg Forthun
> <ingeborg.forthun@gmail.com> wrote:
>> I am sorry if I have misunderstood, but the two codes do not give the
>> same result.
>>
>> The first code:
>> gen n_preg = 0
>> forval j = 95(6)149 {
>>         local J = `j' + 1
>>         replace n_preg = n_preg + inlist(aa`j', 1, 5) | (inlist(aa`j', 2, 3,
>>  4, 6, 7) & inrange(aa`J', 13, .))
>>  }
>>
>> returns:
>>
>>    n_preg |      Freq.     Percent        Cum.
>> ------------+-----------------------------------
>>           0 |     46,703       45.91       45.91
>>           1 |     55,024       54.09      100.00
>> ------------+-----------------------------------
>>       Total |    101,727      100.00
>>
>>
>> The second code:
>> gen n_preg = 0
>> forval j = 95(6)149 {
>>         local J = `j' + 1
>>         replace n_preg = n_preg + 1 if inlist(aa`j', 1, 5) |
>> (inlist(aa`j', 2, 3,
>>  4, 6, 7) & inrange(aa`J', 13, .))
>>  }
>>
>> returns:
>>
>>   n_preg |      Freq.     Percent        Cum.
>> ------------+-----------------------------------
>>           0 |     46,703       45.91       45.91
>>           1 |     35,664       35.06       80.97
>>           2 |     15,164       14.91       95.88
>>           3 |      3,303        3.25       99.12
>>           4 |        682        0.67       99.79
>>           5 |        143        0.14       99.93
>>           6 |         35        0.03       99.97
>>           7 |         19        0.02       99.99
>>           8 |          7        0.01       99.99
>>           9 |          4        0.00      100.00
>>          10 |          3        0.00      100.00
>> ------------+-----------------------------------
>>       Total |    101,727      100.00
>>
>>
>> This is what I need to know. I have to know the exact number of
>> pregnancies and not only 0 or 1.
>>
>> Ingeborg
>>
>> 2012/12/19 Nick Cox <njcoxstata@gmail.com>:
>>> This is likely to be confusing to others.
>>>
>>> As you say, you want to count the number of pregnancies and my code,
>>> along the lines suggested by Daniel, does that. It does that because
>>> the logical condition evaluates to 1 or 0, which gives you the right
>>> answer.
>>>
>>> In a simpler example if you are counting instances of 42 or 43 then
>>>
>>> inlist(42, 42, 43)
>>>
>>> returns 1 and
>>>
>>> inlist (24, 42, 43)
>>>
>>> returns 0  -- so in a loop you can use that result directly. You could
>>> say something like
>>>
>>> replace n42_43 = n42_43 + inlist(<whatever>, 42, 43)
>>>
>>> You don't have to say
>>>
>>> replace n42_43 = n42_43 + 1 if inlist(<whatever>, 42, 43)
>>>
>>> If you want to write it your way, that's fine, but there is no sense
>>> in which you _have_ to do that.
>>>
>>> Nick
>>>
>>> On Wed, Dec 19, 2012 at 9:56 AM, Ingeborg Forthun
>>> <ingeborg.forthun@gmail.com> wrote:
>>>> Thank you very much for your advice!  It works! But as I want to count
>>>> the number of pregnancies for each observation (forgot to write this
>>>> in my first e-mail!) I had to add +1 in the third line in order for it
>>>> to add 1 for each pregnancy.
>>>>
>>>>  gen n_preg = 0
>>>>
>>>> . forval j = 95(6)149 {
>>>>   2.         local J = `j' + 1
>>>>   3.         replace n_preg = n_preg + 1 if inlist(aa`j', 1, 5) |
>>>> (inlist(aa`j', 2, 3, 4, 6, 7) & inrange(aa`J', 13, .))
>>>>   4. }
>>>>
>>>>
>>>>  Ingeborg
>>>>
>>>>
>>>> 2012/12/18 Nick Cox <njcoxstata@gmail.com>
>>>>>
>>>>> I agree with Daniel's main advice. You can simplify this (e.g.)
>>>>>
>>>>> gen n_preg = 0
>>>>> forval j = 95(6)149 {
>>>>>         local J = `j' + 1
>>>>>         replace n_preg = n_preg + inlist(aa`j', 1, 5) | (inlist(aa`j', 2, 3,
>>>>> 4, 6, 7) & inrange(aa`J', 13, .))
>>>>> }
>>>>>
>>>>> See also for specific and general advice:
>>>>>
>>>>> [D]     functions . . . . . . . . . . . . . . .  inlist() programming function
>>>>>         (help inlist())
>>>>>
>>>>> [D]     functions . . . . . . . . . . . . . . . inrange() programming function
>>>>>         (help inrange())
>>>>>
>>>>> SJ-9-1  pr0046  . . . . . . . . . . . . . . . . . . .  Speaking Stata: Rowwise
>>>>>         (help rowsort, rowranks if installed) . . . . . . . . . . .  N. J. Cox
>>>>>         Q1/09   SJ 9(1):137--157
>>>>>         shows how to exploit functions, egen functions, and Mata
>>>>>         for working rowwise; rowsort and rowranks are introduced
>>>>>
>>>>> SJ-6-4  dm0026  . . . . . . Stata tip 39: In a list or out? In a range or out?
>>>>>         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
>>>>>         Q4/06   SJ 6(4):593--595                                 (no commands)
>>>>>         tip for use of inlist() and inrange()
>>>>>
>>>>> It seems also that the names of your variables bear little relation to
>>>>> their contents. Systematic use of -rename- is likely to make further
>>>>> analysis much easier (and less error-prone).
>>>>>
>>>>> Finally, for "STATA" read "Stata", and please read the Statalist FAQ
>>>>> to see why.
>>>>>
>>>>> Nick
>>>>>
>>>>> On Tue, Dec 18, 2012 at 8:47 AM, daniel klein <klein.daniel.81@gmail.com> wrote:
>>>>>
>>>>> > You could probably create a loop over the values 95, 101 and so on,
>>>>> > and add 1 to the respective number inside the loop to get at the
>>>>> > durration. But I would look at -egen-'s -anycount()- function first.
>>>>> > This might be a good way of approching this.
>>>>>
>>>>> Ingeborg Forthun
>>>>>
>>>>> > [...]
>>>>> > I want to make a variable that counts the number of pregnancies for each
>>>>> > woman if outcome is 1 or 5 or if outcome is 2,3,4,6 or 7 and number of
>>>>> > weeks of pregnancy was more than 12 weeks. Number of weeks of
>>>>> > pregnancy is given by aa96 (corresponding to the outcome of the first
>>>>> > pregnancy given by aa95), aa102 (corresponding to the outcome of the
>>>>> > second pregnancy given by aa101), and so on.
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