http://www.iangregory.com/Public ... /base/s/safesum.ado

*! version 3.0.3  28sep2004
program define safesum, rclass
* touched by jwh -- double saves
        version 6.0, missing
        syntax varlist(max=1) [fweight] [if]
        qui summ `varlist' [`weight'`exp'] `if'
        ret scalar sum = cond(r(N)==0 | r(N)==., 0, round(r(sum),1))
        global S_1 `return(sum)'        /* double save */
end
exit