use https://www3.nd.edu/~rwilliam/statafiles/multicoll.dta, clear
corr y x1 x2, means
reg  y x1 x2, beta
vif
vce, corr
* Use collin with uncentered data, the default. (Same as SPSS)
collin x1 x2 if !missing(y)
* Use collin with centered data using the corr option
collin x1 x2 if !missing(y), corr
test x1 = x2
gen x1plusx2 = x1 + x2
reg y x1plusx2

clear all
set obs 5
gen X = _n
gen XSquare = X ^ 2
list
corr X XSquare, means
replace X = X - 3
replace XSquare = X ^ 2
list
corr X XSquare, means