How to generate the column before a column

[Butterfly Poon]

Sorry if this has been asked before
I have dataset containing var1 and var2.
I want to generate a new variable(var3), such that it matches the column before a specific column (var2, in the following case)，where var3=var1

var1	var2	var3
123	AB	123
124	BB	124

Thanks in advance

[Maarten Buis]

generate var3 = var1

[Rich Goldstein]

help clonevar

[Butterfly Poon]

generate var3 = var1

I actually have several groups of var1 var2 var3,
so in fact it is var1 var2 var3 var4 var5 var6 var7 var8

I first hv to identify the maximum value of among var2 var4 var6 var8
and then i want to match the column in front of the max value and generate a new variable

Say, the var4 has the max value among var2 var4 var6 var8
then i want gen(var9), where it is equal to var3


I am thinking about collapsing var1 var2 in a dataset, and then (var3 and var4) in another.... repeatedly and the generate a new column with merge
but it seems too complicated

[Maarten Buis]

You can look at reshaping the data to long format, that should make the task a lot easier. Look at the by prefix maybe combined with egen. I have to pick up the kids now, so I cannot give you more detailed advise.