capture program drop demean

program define demean
	quietly sum `1'
	replace `1'=`1'-r(mean)
end

clear
use /software/stata/auto
demean mpg
sum mpg

capture program drop demean

program define demean
	foreach var of local 0 {
		quietly sum `var'
		replace `var'=`var'-r(mean)
	}
end

clear
use /software/stata/auto
demean mpg price rep78
sum mpg price rep78

clear
use /software/stata/auto
capture noisily demean make mpg price rep78
/* capture noisily tells the command to generate an error message, but not
   crash and stop the rest of the do file. */

sum make mpg price rep78

capture program drop demean

program define demean
foreach var of local 0 {
	capture confirm numeric variable `var'
	if _rc==0 {
		quietly sum `var'
		replace `var'=`var'-r(mean)
	} 
	else di "`var' is not a numeric variable and cannot be demeaned."
}
end

clear
use /software/stata/auto
demean make mpg price rep78
sum make mpg price rep78