Thanks Dennis this is what I was looking for.
On Wed, Jan 26, 2011 at 4:14 AM, Dennis Murphy <djmu...@gmail.com> wrote:
> Hi:
>
> Here's one approach:
>
> f <- function(df) {
> rs <- with(na.exclude(df), tapply(y, strata, sum)/tapply(x, strata,
> sum))
> u <- transform(subset(df, is.na(y)), y = x * rs[strata])
> transform(df, y = replace(y, u$id, u$y))
> }
>
> f(df)
>
> The function works as follows:
>
> (1) With the rows of the data frame where y is not missing,
> find the sum(y)/sum(x) ratio in each stratum. rs is a vector whose
> length is
> the number of strata. (Hopefully, all of your x-sums are nonzero...)
> If you have
> missing x values in your real data, you need to think about how you
> want to
> handle them.
> (2) In a sub-data frame u containing the missing y's, replace them with the
> value of
> x times the value of rs corresponding to its stratum.
> (3) Replace the missing y's in df with the y's from u, matching on id
> numbers. (This
> is a by-product of subset(), BTW.)
>
> HTH,
> Dennis
>
> On Tue, Jan 25, 2011 at 9:40 AM, andrija djurovic <djandr...@gmail.com>wrote:
>
>> Hello R user,
>>
>> I have following data frame:
>>
>> df=data.frame(id=c(1:10),strata=rep(c(1,2),c(5,5)),y=c(
>> 10,12,10,NA,15,70,NA,NA,55,100),x=c(3,4,5,7,4,10,12,8,3,15))
>>
>> and I would like to replace NA's with:
>>
>> instead of first NA
>> tapply(na.exclude(df)$y,na.exclude(df)$strata,sum)[1]*
>> *7 */tapply(na.exclude(df)$x,na.exclude(df)$strata,sum)[1]
>> where 7 is the value of x (id=4) in strata 1 where y=NA
>>
>> instead of second NA
>> tapply(na.exclude(df)$y,na.exclude(df)$strata,sum)[2]*
>> *12 */tapply(na.exclude(df)$x,na.exclude(df)$strata,sum)[2]
>> where 12 is the value of x (id=7) in strata 2 where y=NA
>>
>> instead of third NA tapply(na.exclude(df)$y,na.exclude(df)$strata,sum)[2]*
>> *
>> 8 */tapply(na.exclude(df)$x,na.exclude(df)$strata,sum)[2]
>> where 8 is the value of x(id=8) in strata 2 where y=NA.
>>
>> So, I would like to replace NA inside the stratas on above explained way.
>>
>> Does anyone know how to do this?
>>
>> thanks in advance
>>
>> Andrija
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
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