Double index foreach loop

[Rufus Randolf]

Apologies if this is very rudimentary but what my Googling could uncover I didn't really understand.

Here's a semi-minimal example of what I'm trying to do with two indices:

foreach (i j) in (first 0) (second 1) {
gen `i'=1 if prov==`j'&!missing(age)
recode `i' .=0
gen `i'm=1 if `i'==1&M==1
recode `i'm .=0
gen `i'f=1 if `i'==1&F==1
recode `i'f .=0
}

I'd like i to be first and j to be 0 for one iteration, for the second iteration, I'd like i to be second while j is 1.

[Clyde Schechter]

You can do it this way:

local variables first second
local values 0 1

forvalues n = 1/2 {
    local variable: word `n' of variables
    local value: word `n' of values
    gen `variable' = (prov == `value' & !missing(age))
    gen `variable'm = (`variable' === 1 & M == 1)
    gen `variable'f = (`variable' == 1 & F == 1)
}

There are other ways to do parallel looping, but this is, I think the simplest.

Note also that in general the construction

gen whatever = 1 if some_condition
recode whatever (. = 0)

is more parsimoniously coded as

gen whatever = (some_condition) // OUTER PARENTHESES OPTIONAL, USED ONLY FOR CLARITY

[Rufus Randolf]

That's perfect and thanks for the last little bit of information as well! I had it typed out a very inefficient way but since I'm trying to add the code of my thesis to the appendix, parsimony is very valuable.

[Rufus Randolf]

Ran into an "invalid syntax" error.

Here's my actual code , fiddled around a bit but can't quite see what seems to be the problem.

local variables NL NS NB PEI QC ON MB SK AB BC YNWNT
local values 0 1 2 3 4 5 6 7 8 9 10

forvalues n = 0/10 {
local variable: word `n' of variables
local value: word `n' of values
gen `variable' = (prov == `value' & !missing(age))
gen `variable'm = (`variable' == 1 & M == 1)
gen `variable'f = (`variable' == 1 & F == 1)
}

[Clyde Schechter]

The problem is that in the forvalues loop, n is not a proxy for the values 0 through 10, it is a counter of "words" in the variables and values lists, so it must run from 1 through 11. So on your first time through the loop, with n = 0, you are trying to access word 0 of each list, and there is no such thing. Just change the top of that loop to -forvalues n = 1/11 {- and it'll be fine.

Thanks for posting your exact code so we could see what was going on.

[Rufus Randolf]

Sorry for this problem being a little tedious, I really appreciate the help you're giving me.

I tried running

local variables NL NS NB PEI QC ON MB SK AB BC YNWNT
local values 0 1 2 3 4 5 6 7 8 9 10

forvalues n = 1/11 {
local variable: word `n' of variables
local value: word `n' of values
gen `variable' = (prov == `value' & !missing(age))
gen `variable'm = (`variable' == 1 & M == 1)
gen `variable'f = (`variable' == 1 & F == 1)
}

values not found
r(111);

Additionally, I tried my original syntax error code but with 0 and NL removed and the index still going to 10 and the same error occurred.

[Clyde Schechter]

My error this time. The first two lines inside the loop should be:

local variables: word `n' of `variables'
local value: word `n' of `values'

Note the left quote (`) before and the right quote (') after variables and values, respectively.

Please re-read my explanation in #5. Using -forvalues n = 0/10- will get you nowhere slowly.

[Rufus Randolf]

Applied the method to elsewhere and it cut the code by more than half! Thanks so much.