Extract coefficient and p-value for certain variable from regression loop - loops

Question

In Stata have applied a regression loop to 1000 metabolites (outcome), and the exposure variable is BMI. I also have other variables in the model. I would like to know how I can extract only the coefficient, p-value, and 95% CI for BMI if and only aif BMI is significant. And then I want to extract them into an Excel file.
This is the code I have used. It informed me that there were, for example, 100 significant results. So I'm trying to figure out which 100 are those and extract them for BMI only, without other variables in the model.
local counter = 0
local counter_pos = 0
local counter_neg = 0
foreach outcome of varlist B - Z {
regress `outcome' bmi Age i.sex i.smoking i.lpa2c i.cholestrol
matrix M = r(table)
if M[4, 1] < 0.05 {
local ++counter
if _b[bmi] < 0 {
local ++counter_neg
}
else {
local ++counter_pos
}
}
}
display as text "Total of significant results: " as result `counter'

Answer 1

Here is a reproducible example showing how to send a variable name and some results to a new file. In your case, posting is conditional on a conventionally significant result; here it is unconditional.
sysuse auto, clear
local counter = 0
local negative = 0
local positive = 0
tempname RESULTS
postfile `RESULTS' str32 varname coefficient using myresults.dta, replace
foreach v in price mpg rep78 headroom trunk length turn displacement gear_ratio {
quietly regress `v' weight
local ++counter
if _b[weight] < 0 local ++negative
else local ++positive
post `RESULTS' ("`v'") (_b[weight])
}
di "variables tried: " `counter'
di "negative relation: " `negative'
di "positive relation: " `positive'
postclose `RESULTS'
use myresults, clear
compress
list