Re: st: Count the number of changing string values

[Ching Wong <ching.y.wong@student.adelaide.edu.au>]

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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