Create a cumulative variable

[Giancarlo Carta]

Hi everybody,

I have a panel data and I need to create a new variable based on a dummy variable which varies over time.

In particular the new variable should assume a value equal to the sum of 1 that the dummy variable presents up to the considered year.

I'm trying to obtain a database like the following:

PRODUCT	ORIGIN	YEAR	VARIABLE X	NEW VARIABLE
A	BG	1995	0	0
A	BG	1996	1	1
A	BG	1997	0	1
A	BG	1998	1	2
A	BG	1999	1	3
B	BG	1995	1	1
B	BG	1996	0	1
B	BG	1997	1	2
B	BG	1998	1	3
B	BG	1999	1	4
A	MI	1995	0	0
A	MI	1996	0	0
A	MI	1997	1	1
A	MI	1998	0	1
A	MI	1999	0	1

Thanks in advance

Giancarlo

[Nick Cox]

 
help sum()

[Carlo Lazzaro]

Giancarlo:
expanding on Nick's sound advice, what follows will do the trick:

bysort product  origin : g newvariable= sum(variablex)

[Giancarlo Carta]

Thank you both I have applied:

xtset pairid Year (pairid is an indicator for each threesome of orig dest and product)

and then:

by pairid: g newvari =sum(variablex)

Thank you very much

[Carlo Lazzaro]

Giancarlo.
thanks for closing the thread with this good news.