Gravity model , Fot( frequency of trade)

[KIM SUJIN]

Dear all!

Hello! here is Sujin,

Im covering trade panel data between 100 import, export countries.

I have trade data which is 1 if trade value>0 , 0 if trade value= 0

I hope to get accumulated frequency data for each country combination


For example, US, Canada had a data (if they only had trade 2000,2001)

import, export, year, trade(0 or 1) ,accumulated frequency
US, Cananda,2000, 1, 1
US,Canada, 2001, 1, 2
US, Canada, 2002, 0, 2


I hope to make accumulated frequency
but I do not know command!!

If any of you know about it,

If you share information
It would be really grateful and appreciated

Thank you
Sujin

[Joao Santos Silva]

Look at the egen command with the by prefix.

All the best,

Joao

[KIM SUJIN]

Thank you
Prof.Joao Santos Silva!



My data variables are
import country, export country, value, year period,

I used command

collapse (sum) Value_, by(YearPeriod country )
sort country Year

bysort(country): egen example=sum(Value_)

but I got 'invalid syntax' sign.

And I wonder which part is wrong


Thank you so much!

[Joao Santos Silva]

Sorry, I am not familiar with those commands; hopefully someone else will help.

Best wishes,

Joao

[KIM SUJIN]

Thank you so much!!

[Jorrit Gosens]

This works, but only if there are no duplicate observations for each combination of import, export and year.

* Example generated by -dataex-. To install: ssc install dataex
clear
input str6(export import) float(year trade)
"US" "Canada" 2000 1
"US" "Canada" 2001 1
"US" "Canada" 2002 0
end

bys export import (year): gen acfreq = trade if _n==1
bys export import (year): replace acfreq = trade + acfreq[_n-1] if _n!=1

Also, for future posts, please use dataex to provide a data example. This makes it tons easier for people to answer your question. See more on why and how in the FAQ: https://www.statalist.org/forums/help#stata

[KIM SUJIN]

It works!! Thank you so much!!