### Wednesday, March 15, 2006

## st: Re: summing up digits and comparing to a check digit

I'm not sure I understand the problem -- one of your examples is an 8 digit number but you say you have 7 digit numbers. Anyway, here is some "highly advanced programming" (?) :

gen x=string(myvar) replace x="0"+x if length(x)==6 gen check=mod(real(substr(x,2,1))+real(substr(x,3,1))+real(substr(x,4,1))+real(substr(x,5,1))+real(substr(x,6,1))+real(substr(x,7,1)),10)

make sure to remove any line break that the email puts in the last line.

Michael Blasnik

----- Original Message ----- From: "Lia Orfei" <lorfei@sgul.ac.uk> To: <statalist@hsphsun2.harvard.edu> Sent: Wednesday, March 15, 2006 9:54 AM Subject: st: summing up digits and comparing to a check digit

> Dear all, > Here is a highly advanced programming challenge for you (!) > > I have a variable that contains 7-digit numbers; the first digit is the > remainder of the sum of the last six digits divided by 10 (check digit) > > example: 1030332 => 0+3+0+3+3+2=11/10=1+1 => check digit=1 > 12050457 => 0+5+0+4+5+7=21/10=2+1 => check digit=1 > and so on. > > Now I want to assess whther the check digit is correct for each entry. > > How do I calculate the partial sum of the contents of this variable? > > Extra challenge: some of the numbers sum up to 10, 20 etc so the check > digit is actually 0 and it does not appear in the data for some reason > (example 50456 is correct becasue 5+0+4+5+6=20 so the remainder is 0). > > Any ideas?? I was thinking about using the string functions. > > Thanks a lot > > Lia

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