Re: st: Count the number of changing string values

[Nick Cox <njcoxstata@gmail.com>]

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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