CODEWITHSUNDEEP
statadata-manipulation
Sunv
Sunv

Reputation: 237

Creating indicator variable in Stata

In a panel data set I have 3 variables: name, week, and income.

I would like to make an indicator variable that indicates initial weeks where income is 0. So say a person X has 0 income in the first 13 weeks, the indicator takes the value 1 the first 13 weeks, and is otherwise 0. The same procedure for person Y and so on.

I have tried using by groups, but I can't get it to work.

Any suggestions?

Upvotes: 0

Views: 171

Answers (1)

Nick Cox
Nick Cox

Reputation: 37208

One solution is 

bysort name (week) : gen no_income = sum(income) == 0

The function sum() yields cumulative or running sum. So, as long as income is 0, its cumulative sum remains 0 too. As soon as a person earns something, the cumulative sum becomes positive. The code is based on the presumption that cumulative income can not cross zero again because in a given week, income is negative. To exclude that possibility use an appropriate extra condition, such as 

bysort name (week) : gen no_income = sum(income) == 0 & income == 0

For a problem with very similar flavour, see this FAQ. A meta-lesson is to look at the StataCorp FAQs as one of several resources.

Upvotes: 2

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