Re: st: Merging consecutive spells with the same value of Y

[Nick Cox <njcoxstata@gmail.com>]

Assuming no gaps

bysort ID (Start) : gen Spell =  sum(Y != Y[_n-1])
collapse (min)Start (max)End Y, by(ID Spell)

Nick
njcoxstata@gmail.com


On 17 June 2013 11:07, Kai Huang <demonsecret@hotmail.com.hk> wrote:
> Dear all,
>
> I have a spell dataset as follows:
>
> ID   Start   End     Y
> 888  1981    1985    0
> 888  1985    1989    2
> 888  1989    1991    1
> 888  1991    1995    1
> 888  1995    1997    1
> 888  1997    2000    2
> 890  1985    1987    2
> 890  1987    1991    0
> 890  1991    1994    0
> 890  1994    1997    1
> I hope to merge consecutive spells with the same value of Y, so that the data becomes as follows:
> ID   Start   End     Y
> 888  1981    1985    0
> 888  1985    1989    2
> 888  1989    1997    1
> 888  1997    2000    2
> 890  1985    1987    2
> 890  1987    1994    0
> 890  1994    1997    1
>
> I use the following commands, but can only achieve my aim for ID 890:
> by ID: replace End = End[_n+1] if EconActivity==0 & EconActivity[_n+1]==0
> by ID: drop if End == End[_n-1] & Start>Start[_n-1] & EconActivity==EconActivity[_n-1]==0
> by ID: replace End = End[_n+1] if EconActivity==1 & EconActivity[_n+1]==1
> by ID: drop if End == End[_n-1] & Start>Start[_n-1] & EconActivity==EconActivity[_n-1]==1
>
> I wonder how I can merge all consecutive spells with the same value of Y, even if the number of consecutive spells are more than 2? Thank you very much in advance.
>
> Best regards,
> Kai Huang
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