Stepping (?) Loop.

[Muh-Chung Lin]

Dear Stata Users:

I am using Stata 15 and having some problems in writing loops that do not loop over the previous value. Specifically, my loop looks like:

foreach i of numlist 1/10 {
replace z=1 if x`i'=1 & y=i+1
}

In other words, I would like to start to change z to 1 if x1=1 & y=2 ... 11. For the next round, I would like to start from x2=1 & y=3. And so forth. I have also experimented with the following loop:

foreach i of numlist 1/10 {
forval j=i+1 {
replace z=1 if x`i'=1 & y=`j'
}
}

Neither worked. I have searched the forum as well as elsewhere on the Internet, but could not find a solution. Maybe the terminology I used in search was wrong. I have also read Stata programming book, but could not find it. I know this probably could be solved using "while" or macro/micro, but I would like to know how this could be done using just foreach or forvalue.

Thank you very much in advance.

Sincerely,
Muh-Chung Lin

[Nick Cox]

I guess you want

foreach i of numlist 1/10 {
replace z=1 if x`i'==1 & y==`i'+1
}

or more simply

forval  i = 1/10 {
replace z=1 if x`i'==1 & y==`i'+1
}

Your existing code is checking for a variable named i -- not the macro i defined by the loop. Your attempted fix fails for essentially the same reason

If you really wrote = where == is needed then your code would fail for that reason too.

[Muh-Chung Lin]

Dear Mr. Cox:

Yes. That works. It is exactly the lack of "` ' " after the equation that made them not work.

Thank you VERY MUCH!!

Sincerely,
Muh-Chung Lin