why dont you use "Amelia"? 
It's an R package which deal with missing data in R
http://gking.harvard.edu/amelia/


Ferdinand Alimadhi wrote:

>You can deal with the missing values before performing any regression model.
>if you dataset is :
>
> > D
>  X1 X2 X3
>1 NA  2  4
>2  1 NA NA
>3  2  2  6
>4 NA 34 NA
>5  3 NA  7
>
>then the following will replace all NA with the mean value
>
> > f<-function(col){
>+ col[is.na(col)]<-mean(col,na.rm=TRUE)
>+ col}
> > sapply(D,f)
>     X1       X2       X3
>[1,]  2  2.00000 4.000000
>[2,]  1 12.66667 5.666667
>[3,]  2  2.00000 6.000000
>[4,]  2 34.00000 5.666667
>[5,]  3 12.66667 7.000000
>
>
>Hope this is what you want.
>
>zhijie zhang wrote:
>
>  
>
>>Dear Rusers,
>>The default behavior in R when performing a regression model with missing
>>values is to exclude any case that contains a
>>missing value? How could i set the bahavior that R deal with missing values?
>>e.g.:
>>exclude cases listwise
>>exclude cases pairwise
>>replace with mean
>>
>>Thanks very much!
>>
>> 
>>
>>    
>>
>
>
>  
>


-- 
Ferdinand Alimadhi
Programmer / Analyst
Harvard University
The Institute for Quantitative Social Science
(617) 496-0187
falimadhi@iq.harvard.edu
www.iq.harvard.edu


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