Many thanks to Austin, Klaus, and Svend for explaining to me.
I found it especially helpful when example syntax and the associated
terminologies such as explicit subscripting were referred in your
responses. I was able to find further information and applied them
correctly. --- Chiung-Ya
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Below is a summary of approaches to my question.
In order to generate v2 as presented below
ID Member v1 v2
1 1 3.2 4.5
1 2 4.5 3.2
2 1 3.1 3.3
2 2 3.3 3.1
3 1 . 2.3
3 2 2.3 .
Austin suggested:
bys ID (Member): g v2=v1[3-_n]
and Klaus and Svend shared their approaches:
gen v2=.
by ID, sort: replace v2=v1[_n+1] if v2==.
by ID: replace v2=v1[_n-1] if v2==.
sort ID Member
generate v2=v1[_n+1] if ID==ID[_n+1] & Member==1
replace v2=v1[_n-1] if ID==ID[_n-1] & Member==2
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