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Re: st: SUM question


From   David Bell <dcbell@iupui.edu>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: SUM question
Date   Thu, 15 May 2008 08:39:03 -0400

Dear Satomi,

You have surmised that -egen newvar = rowtotal(var1 var2)- treats missing values as zero. I do not believe this is strictly correct. The command just sums the values that it has (thus not using a variable in a sum is the same as treating it as zero). This is why I always use -rowmean- instead of -rowtotal-. Thus when there is a missing value, you get the mean of the remaining values (they are not treated as zeros).

Dave
====================================
David C. Bell
Professor of Sociology
Indiana University Purdue University Indianapolis (IUPUI)
(317) 278-1336
====================================




On May 15, 2008, at 12:31 AM, Yamamoto, Satomi wrote:


Hello,

Thank you very much for the prompt reply.
I think egen newvar = rowtotal(var1 var2) is equivalent to replacing missing values with 0(zero).

The SUM function in SPSS adds cases in the variable where at least one observation is valid:

Var 1 Var2
1 4
3 5
4 5
5 8
. 5
. .

When compute newvar= sum(var1, var2). is used, there will be 1 missing case.
When compute newvar= var1+var2. is used, there are 2 missing cases.

Do you have any ideas? It would be great if I could get help on this.

Sincerely,
Satomi


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu ] On Behalf Of Richard Williams
Sent: Wednesday, May 14, 2008 11:47 PM
To: statalist@hsphsun2.harvard.edu; statalist@hsphsun2.harvard.edu
Subject: Re: st: SUM question

At 10:29 PM 5/14/2008, Yamamoto, Satomi wrote:

Hello,

I'm wondering if anybody knows the Stata command that is equivalent to
the following SPSS command:

compute newvar= sum(var1, var2).
exe.

The SUM function in SPSS allows you to keep cases with missing values
instaead of droppoing them. It's one way of preventing listwise
deletion. It would be great if I can get help with this.

Sincerely,
Satomi
egen newvar = rowtotal(var1 var2)


-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME:   (574)289-5227
EMAIL:  Richard.A.Williams.5@ND.Edu
WWW:    http://www.nd.edu/~rwilliam

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