Generate variable which count and sum

[Guest]

Hello Stata users!
I think the following is a very easy question, but I'm just a beginner with Stata so I'm trying to learn more and more everyday! :-)
I have the following variables in my dataset:

ID_Family	N_components	Income
1	3	0
1	3	1000
1	3	0
2	4	10000
2	4	500
2	4	0
2	4	3500
3	1	20000
4	2	5000
4	2	0

It is a survey with ID of the family interviewed, the number of components of each family, and the income of each person.
I would like to create a new variable (Fam_income) that for each component reports the family's income (as a sum of the income of each component)
Just like that:

ID_Family	N_components	Income	Fam_income
1	3	0	1000
1	3	1000	1000
1	3	0	1000
2	4	10000	14000
2	4	500	14000
2	4	0	14000
2	4	3500	14000
3	1	20000	20000
4	2	5000	5000
4	2	0	5000

Someone can help me, please?
Thanks in advance!

[Nick Cox]

student90: The request to you voiced by Carlo Lazzaro on 19 January 2015 that you use a full real name still stands. Please see

http://www.statalist.org/forums/help#realnames

http://www.statalist.org/forums/help#adviceextras Section 3

* read the help first
help egen

bysort ID_Family: egen Fam_income = total(Income)