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Re: st: Count the number of changing string values


From   Sergiy Radyakin <serjradyakin@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Count the number of changing string values
Date   Fri, 14 Jun 2013 08:20:47 -0400

clear
input  Id     str1 sex   drug1999   drug2000    drug2001      drug2002
1       F       1            0          1            .
3       M       0           1          1             0
5      F         1          1          1            1
9      M       .    1          0             1
10     F        1           0           1             0
end
list

generate c=0

forval y=1999/2001 {
  replace c=c+cond((drug`y'-drug`=`y'+1')^2<=1,(drug`y'-drug`=`y'+1')^2,0)
}

list

On Fri, Jun 14, 2013 at 7:50 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> Fine. If you tell me what your data are  once -reshape-d I will advise.
>
> Nick
> njcoxstata@gmail.com
>
>
> On 14 June 2013 12:45, 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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