Re: st: SUM question

[David Bell <dcbell@iupui.edu>]

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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