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I would like to calculate the sum of variable boasav:

clear

input id boasav
1 2500
1 2900
1 4200
2 5700
2 6100
3 7400
3 7600
3 8300
end

I know that the tabulate command can be used to summarize data but it only counts:

bys id: tab boasav 

-> id = 1

 boasav | Freq. Percent Cum.
------------+-----------------------------------
 2500 | 1 33.33 33.33
 2900 | 1 33.33 66.67
 4200 | 1 33.33 100.00
------------+-----------------------------------
 Total | 3 100.00

-> id = 2

 boasav | Freq. Percent Cum.
------------+-----------------------------------
 5700 | 1 50.00 50.00
 6100 | 1 50.00 100.00
------------+-----------------------------------
 Total | 2 100.00

-> id = 3

 boasav | Freq. Percent Cum.
------------+-----------------------------------
 7400 | 1 33.33 33.33
 7600 | 1 33.33 66.67
 8300 | 1 33.33 100.00
------------+-----------------------------------
 Total | 3 100.00

However, what I want is the following:

1 9600 
2 11800 
3 23300 

Is there a function that can do this in Stata?

Solution 1: calculate and present using the list or table commands

bysort id: list, sum(boasav)

-> id = 1
 +-------------+
 | id boasav |
 |-------------|
 1. | 1 2500 |
 2. | 1 2900 |
 3. | 1 4200 |
 |-------------|
 Sum | 9600 |
 +-------------+

-> id = 2
 +-------------+
 | id boasav |
 |-------------|
 1. | 2 5700 |
 2. | 2 6100 |
 |-------------|
 Sum | 11800 |
 +-------------+

-> id = 3 
 +-------------+
 | id boasav |
 |-------------|
 1. | 3 7400 |
 2. | 3 7600 |
 3. | 3 8300 |
 |-------------|
 Sum | 23300 |
 +-------------+

table id, contents(sum boasav)

-----------------------
 id | sum(boasav)
----------+------------
 1 | 9600
 2 | 11800
 3 | 23300
-----------------------

Solution 2: generate extra variables with the results and then list

bysort id (boasav): generate sum1 = sum(boasav)

or

by id: egen sum2 = total(boasav)

Both of these approaches will produce the same results:

by id: list sum* if _n == _N

-> id = 1 
 +-------------+
 | sum1 sum2 |
 |-------------|
 3. | 9600 9600 |
 +-------------+

-> id = 2 
 +---------------+
 | sum1 sum2 |
 |---------------|
 2. | 11800 11800 |
 +---------------+

-> id = 3 
 +---------------+
 | sum1 sum2 |
 |---------------|
 3. | 23300 23300 |
 +---------------+

Solution 3: create a new dataset with the results and list

collapse (sum) boasav, by(id)
list

 +-------------+
 | id boasav |
 |-------------|
 1. | 1 9600 |
 2. | 2 11800 |
 3. | 3 23300 |
 +-------------+

Note that this last solution will destroy your current dataset.

Here are three more.

clear

input id boasav
1 2500
1 2900
1 4200
2 5700
2 6100
3 7400
3 7600
3 8300
end

* Method 4: use summarize 

forval g = 1/3 
 su boasav if id == `g', meanonly 
 di "`g' " %5.0f r(sum) 
 

1 9600
2 11800
3 23300


* Method 5: tabstat 

tabstat boasav, by(id) stat(sum) 

Summary for variables: boasav
 by categories of: id 

 id | sum
---------+----------
 1 | 9600
 2 | 11800
 3 | 23300
---------+----------
 Total | 44700
--------------------


* Method 6: use rangestat (SSC) 

rangestat (sum) boasav, int(id 0 0)

tabdisp id, c(boasav_sum)

-------------------------
 id | sum of boasav
----------+--------------
 1 | 9600
 2 | 11800
 3 | 23300
-------------------------