How to claculate the accumulative value

[ALKEBSEE RADWAN]

Dear All

I am collecting some data. this data needs a calculation process
I do understand the process but I don't know to do do a part of it.

The equaion as follows
ARi,t= Ri,t - MRt .....(1)
where is i stands for a firm, and t for the date. Ri,t is daily return, MR is the markt return.
Each firm or event (M&A) for each firm has even-dates like a range of time for example 5 or 10 days.

Firm R MR evendate

1 1.5 2 1-05-2021
1 2 2 2-05-2021
1 1 2 3-05-2021
1 0.5 2 4-05-2021
1 3 2 5-05-2021

in Eq.(1) AR refers to the abnormal return after M&A.
According to this I will have for example five values of ARi,t for each firm.
Then I want to calculate the Accumulative ARi,t

My question is whcih command for this
I know that the accumulative value is calculated by adding the previous values to the current one so on.
But here I have to limit it based on the evendate variable
please someone give me the command for this

Best,

[Andrew Musau]

The -sum()- function of generate calculates a running sum, while the -bysort- prefix restricts the calculation to each group.

* Example generated by -dataex-. For more info, type help dataex
clear
input byte firm double r byte mr str9 evendate
1 1.5 2 "1-05-2021"
1   2 2 "2-05-2021"
1   1 2 "3-05-2021"
1  .5 2 "4-05-2021"
1   3 2 "5-05-2021"
end

gen edate= daily(evendate, "DMY"), after(firm)
format edate %tdD-N-CY
bys firm (edate): gen wanted= sum(r - mr)

Res.:

. l, sepby(firm)

     +---------------------------------------------------+
     | firm        edate     r   mr    evendate   wanted |
     |---------------------------------------------------|
  1. |    1   01-05-2021   1.5    2   1-05-2021      -.5 |
  2. |    1   02-05-2021     2    2   2-05-2021      -.5 |
  3. |    1   03-05-2021     1    2   3-05-2021     -1.5 |
  4. |    1   04-05-2021    .5    2   4-05-2021       -3 |
  5. |    1   05-05-2021     3    2   5-05-2021       -2 |
     +---------------------------------------------------+

[ALKEBSEE RADWAN]

The sum command calculates a running sum, while the -bysort- prefix restricts the calculation to each group.

* Example generated by -dataex-. For more info, type help dataex
clear
input byte firm double r byte mr str9 evendate
1 1.5 2 "1-05-2021"
1 2 2 "2-05-2021"
1 1 2 "3-05-2021"
1 .5 2 "4-05-2021"
1 3 2 "5-05-2021"
end

gen edate= daily(evendate, "DMY"), after(firm)
format edate %tdD-N-CY
bys firm (edate): gen wanted= sum(r - mr)

Res.:

. l, sepby(firm)

+---------------------------------------------------+
| firm edate r mr evendate wanted |
|---------------------------------------------------|
1. | 1 01-05-2021 1.5 2 1-05-2021 -.5 |
2. | 1 02-05-2021 2 2 2-05-2021 -.5 |
3. | 1 03-05-2021 1 2 3-05-2021 -1.5 |
4. | 1 04-05-2021 .5 2 4-05-2021 -3 |
5. | 1 05-05-2021 3 2 5-05-2021 -2 |
+---------------------------------------------------+

Thank you very much

[Andrew Musau]

Note the correction in #2: It should read "the -sum()- function of generate".