Storing outputs of multiple regressions run in loop in single dta file

[Emory Davis]

I am using a loop to run multiple mixed effect linear regression models, to see the effect of the same two independent variables on multiple dependent variables. Here is a sample of my data (it only includes a subset of the variables that I am using as dependent variables in the model):

* Example generated by -dataex-. For more info, type help dataex
clear
input float(form title1 rrate1) long(acad1 acad2 stat2 stat3)
1 0 100 4 3 4 3
1 0 100 4 1 1 1
1 0 100 4 3 4 3
1 0 100 4 3 4 .
1 0 100 3 2 2 2
1 0 100 4 4 4 4
1 0 100 4 2 3 4
1 0 100 4 4 4 4
1 0 100 4 4 4 4
1 0 100 3 4 2 2

Here is the loop I've written (I've used capture because some variables that start with acad have no observations for the subset of data specified by if form==1):

foreach i of varlist acad* stat* {
    display "`i'"
    capture noisily mixed `i' i.title1 rrate1  if form==1 || school:
}

I would like to save the output of each regression in a dta file, with the output looking something like this:

DV name	IV name	Coeff	SE	z	p
acad1	title1 yes	xxx	xxx	xx	xx
acad1	rrate	xxx	xxx	xxx	xx
acad2	title1 yes	xxx	xxx	xxx	xxx
acad2	rrate2	xxx	xxx	xxx	xxx

I've tried -statsby- (see below) but I don't think it can accomplish what I want, unless I'm not fully understanding what it's capable of. First, I don't actually need to run a regression for each value of the variable 'form' (I only need to run it for form==1) but statsby requires a grouping variable. Second, it ignores capture so I have to specify each variable so that the loop doesn't error out - ok, fine, I have to do some extra typing. Third, the save option only saves the output of each individual regression (although that's really more how the loop is written).

foreach i of varlist acad1 acad2 acad3 acad6 acad7 acad8 acad9 acad10 stat2 stat3 {
    display "`i'"
    statsby, by(form) saving(".do Files/Reporting/Insights Report/Working Files/myest.dta"): mixed `i' i.title1 rrate1 || school:
}

What I need is some way to append the results of each regression (ultimately, I will be running dozens of regressions) within the loop, so that only one dta file is created. I have done lots of searching and reading past posts, and I'm sure there is a solution but I haven't found one, at least one I could understand and translate to my situation - I am still relatively new to Stata.

I am using Stata 17.

[Clyde Schechter]

Duplicate post. Asked and answered at https://www.statalist.org/forums/for...ingle-dta-file.