Compute the Partial sum of a Variable within Group in Stata?

[smith Jason]

I have a small dataset as follows,
clear
input schid person_id math_score
1 1 89
1 11 67
1 12 99
2 1 100
2 11 88
2 12 85
2 13 95
end
I want to create a new variable called partial_sum, which should be equal to the sum of the values of math_score except for the 1st observation within schid. For example, when schid=1, the partial_sum=67+99=176; when schid=2, the partial_sum=88+85+95=268 Can someone help me with the Stata code? Thank you!

[Carlo Lazzaro]

Jason:
do you mean something along the following lines?

. bysort schid: egen wanted=total( math_score) if _n>1


. list

     +--------------------------------------+
     | schid   person~d   math_s~e   wanted |
     |--------------------------------------|
  1. |     1          1         89        . |
  2. |     1         11         67      166 |
  3. |     1         12         99      166 |
  4. |     2          1        100        . |
  5. |     2         11         88      268 |
     |--------------------------------------|
  6. |     2         12         85      268 |
  7. |     2         13         95      268 |
     +--------------------------------------+

.

[smith Jason]

Thank you! If I want the missing value is replaced by the computed sum, could you please help me with your code?

[Carlo Lazzaro]

Jason:

. bysort schid: replace wanted=wanted[2] if wanted==.


. list

     +--------------------------------------+
     | schid   person~d   math_s~e   wanted |
     |--------------------------------------|
  1. |     1          1         89      166 |
  2. |     1         11         67      166 |
  3. |     1         12         99      166 |
  4. |     2          1        100      268 |
  5. |     2         11         88      268 |
     |--------------------------------------|
  6. |     2         12         85      268 |
  7. |     2         13         95      268 |
     +--------------------------------------+

.

[smith Jason]

Thank you!