STATA: Replicate interpolation for multiple variables

Question

I am interpolating multiple variables, but don't know how to do it efficiently.

My data looks like this

Country	Year	v_country_1	v_country_2	v_country_3	...	v_country_234
Canada	2000	1005	1051	1052	---	1120
Canada	2001				---
Canada	2002				---
Canada	2003				---
Canada	2004	2000	3500	500	---	10562
Korea	2000	1005	1051	1052	---	1120
Korea	2001				---
Korea	2002				---
Korea	2003				---
Korea	2004	2000	3500	500	---	10562
...	...	...	...	...	---	....
Uganda	2000	1005	1051	1052	---	1120
Uganda	2001				---
Uganda	2002				---
Uganda	2003				---
Uganda	2004	2000	3500	500	---	10562

As you can see my data includes multiple countries. So, I need to interpolate the variables by country.

I can interpolate the one variable very easily by using the code:

by cow: ipolate v_country_1 year, gen(v_country_1_ipo)

But, I have 234 variables... so it is almost impossible to replicate this work by hand.

Could you please teach me how to do it? (I know there is a command foreach that is meant to do replication.)

Answer 1

ds v_country_*

foreach x in `r(varlist)' {
    by country: ipolate `x' year, gen(`x'_ipo)
}

// OR

forvalues i = 1/234 {
    by country: ipolate v_country_`i' year, gen(v_country_`i'_ipo)
}

Check out help ds and help forvalues or help foreach for further details.