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Re: st: Count the number of changing string values


From   Ching Wong <ching.y.wong@student.adelaide.edu.au>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Count the number of changing string values
Date   Fri, 14 Jun 2013 21:19:20 +0930

Sorry, Nick.
I ask again.

I would to identify "the first year in which a user said Yes after
previously saying No".


Because I only concern the FIRST one.


Ching

On 14 June 2013 21:15, Ching Wong <ching.y.wong@student.adelaide.edu.au> wrote:
> Hi Nick,
>
> I would like to count "how many times a user said Yes one year and No the next".
>
> Thanks.
>
> Ching
>
> On 14 June 2013 21:11, Nick Cox <njcoxstata@gmail.com> wrote:
>> I take this to be a new question, but I am unclear what you want. Do you want
>>
>> 1. Counting how many times a user said Yes one year and No the next?
>>
>> 2. Identifying the first year in which a user said Yes after
>> previously saying No.
>>
>> I fall back on emphasising my previous advice
>>
>> Long structure ... is likely to be better for you for most analyses.
>>
>> Get these data -reshape-d. You are going to want to do lots of
>> analyses on different kinds of patterns, and keeping this structure is
>> really going to strain any user's Stata fluency.
>>
>> Nick
>> njcoxstata@gmail.com
>>
>>
>> On 14 June 2013 12:12, Ching Wong <ching.y.wong@student.adelaide.edu.au> wrote:
>>> Thanks Nick
>>>
>>> Yes, it's all good if I only need to count the first "NO'.
>>>
>>> But I would rather to see how to count the first "YES & NO" between
>>> year of study.
>>>
>>> id Drug2009   Drug 2000
>>> 1    Yes              NO      ------->ONE count
>>>
>>> Regards,
>>>
>>> Ching
>>>
>>> On 14 June 2013 20:24, Nick Cox <njcoxstata@gmail.com> wrote:
>>>> I can't see your value labels from here. But suppose that "No" is a
>>>> label for value 1.
>>>>
>>>> replace year = `j' if  Drug`j' == 1 & missing(year)
>>>>
>>>> I trust that you will be able to modify that to your situation.
>>>>
>>>>
>>>> Nick
>>>> njcoxstata@gmail.com
>>>>
>>>>
>>>> On 14 June 2013 11:45, Ching Wong <ching.y.wong@student.adelaide.edu.au> wrote:
>>>>> Hi Nick,
>>>>>
>>>>> So what if -drug*- are numeric variables with value labels, how should
>>>>> I change my Command?
>>>>>
>>>>>
>>>>> Thanks!
>>>>>
>>>>>
>>>>> Ching
>>>>>
>>>>> On 14 June 2013 19:19, Nick Cox <njcoxstata@gmail.com> wrote:
>>>>>> Code that "doesn't work" but is not shown can not be commented on.
>>>>>> Long structure (I prefer to avoid the word "format" here) is not
>>>>>> essential for the problem as I understand it, but it is likely to be
>>>>>> better for you for most analyses.
>>>>>>
>>>>>> The year in which people first said "No" is
>>>>>>
>>>>>> gen year = .
>>>>>>
>>>>>> qui forval j = 1999/2012 {
>>>>>>         replace year = `j' if  Drug`j' == "No" & missing(year)
>>>>>> }
>>>>>>
>>>>>> tab year
>>>>>>
>>>>>> So,
>>>>>>
>>>>>> 1. Everybody starts out with missing.
>>>>>>
>>>>>> 2. If they said "No" in 1999, -year- is changed to 1999
>>>>>>
>>>>>> 3. If they said "No" in 2000, -year- is changed to 2000, but only if
>>>>>> -year- is missing (so values of 1999 are protected)
>>>>>>
>>>>>> and so on.
>>>>>>
>>>>>> You didn't explain your datatypes. If -drug*- are numeric variables
>>>>>> with value labels, the syntax will differ accordingly.
>>>>>>
>>>>>> Nick
>>>>>> njcoxstata@gmail.com
>>>>>>
>>>>>>
>>>>>> On 14 June 2013 10:20, Ching Wong <ching.y.wong@student.adelaide.edu.au> wrote:
>>>>>>
>>>>>>> I have the following data set:
>>>>>>>
>>>>>>> Id     sex   drug1999   drug2000    drug2001      drug 2001
>>>>>>>
>>>>>>> 1       F       Yes            No          Yes            Unknown
>>>>>>>
>>>>>>> 3       M       No           Yes          Yes             No
>>>>>>>
>>>>>>> 5      F         Yes          Yes          Yes            Yes
>>>>>>>
>>>>>>> 9      M       Unknown    Yes          No             Yes
>>>>>>>
>>>>>>> 10     F        Yes           No           Yes             No
>>>>>>>
>>>>>>> I would like to produce a count of to show the number of people who
>>>>>>> quit each year, only count the first time they quit and do not care if
>>>>>>> they change their status to ‘No’ again.
>>>>>>>
>>>>>>> What would be the command? I tried to change it to the long formal and
>>>>>>> use the lag function, but it doesn’t work.
>>>>>>
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