Intersection among datasets

[Federico Nutarelli]

Hi all,

so I have k databases (55) called name_country_mole.dta. Each database is an unbalanced panel of molecules observed for a certain number of quarters (the number of quarters and the quarters themselves might vary from a database to another). My objective is to find the matching molecules and quarters (i.e. intersection) across those datasets. When I had only 3 or 4 countries what I did was simply a series reclink of the type:

reclink Molecule quarter using "france_mole.dta", gen(myscore) idm(id_mas) idu(id_us) minscore(1)

so country1 reclinked with country2 obtaining the data countr1_2.dta. Then country_1_2.dta reclinked with country3 to obtain country_1_2_3.dta and so on. Now that I have 55 databases have to find a smarter way to perform such a task.
Can anyone please help me? I was thinking about something involving tempfiles but I am new to these.

Thank you,

Federico

[Joseph Coveney]

Is there a reason why you wouldn't consider -merge-?

cd <whatever>
local file_list : dir "`c(pwd)'" files "*_mole.dta"

local first 1

tempfile accumulation

foreach file of local file_list {

    use "`file'"

    if !`first' merge 1:1 Molecule quarter using `accumulation', keep(match) nogenerate noreport
    else local first 0

    quietly save `accumulation', replace

}

[Federico Nutarelli]

Joseph Coveney thank you for your reply.

Is there a reason why you wouldn't consider -merge-?

Actually because they are unbalanced panels and the way in which they are unbalanced is unknown to me (data collection issues). Therefore, I don't have the same number o observations in each dataset nor the same molecules. Also, I am not sure that merge keeps only the Molecules and quarters in common as reclink does.

[Joseph Coveney]

You said, "My objective is to find the matching molecules and quarters (i.e. intersection) across those datasets."

merge <cardinality> Molecules quarters using <datasets>, keep(match)

is exactly how you do that.

[Federico Nutarelli]

Joseph Coveney I did not know it. Thank you