Hello Statalists,
Please, could anyone help with the correct command?
I have two datasets measuring the weight of a product using two different methods. I want to know the correlation between this two variables called 'grams1' and 'grams2'.
The two data sets have the same id variable, the same time var and the grams var differ between both data. The two data sets samples and my codes are below. Is this the correct way to assess the correlation between this two variables? What I expect is that the correlation is very high indicating that both weighting methods are similar and yield close weight in grams.
Thank you!

Grams1.dta

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id grams1 time)
11 13 1
11 12 2
11 19 3
22 21 1
22 10 2
22 15 3
33 35 1
33 29 2
33 20 3
end

Grams2.dta

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id grams2 time)
11   21 1
11   12 2
11   18 3
22 21.5 1
22   11 2
22 14.7 3
33   36 1
33   29 2
33 20.6 3
end

I then tried to do the following:
Code:
use grams1,clear
sort id time
merge 1:1 id time using grams2
I get the following merged dataset:
Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id grams1 time grams2) byte _merge
11 13 1   21 3
11 12 2   12 3
11 19 3   18 3
22 21 1 21.5 3
22 10 2   11 3
22 15 3 14.7 3
33 35 1   36 3
33 29 2   29 3
33 20 3 20.6 3
end
label values _merge _merge
label def _merge 3 "matched (3)", modify
And finally I did:
Code:
pwcorr grams1 grams2, star(0.01)