[R] vectorization

[Liaw, Andy]

Here I go again with ave():

mydata$md <- ave(mydata$income, mydata$education, FUN=median, na.rm=TRUE)

IMHO it's one of the most under-rated helper functions in R.

Andy

> From: Dimitri Joe
> 
> Hi there,
> 
> I have a data frame (mydata) with 1 numeric variable (income) 
> and 1 factor (education). I want a new column in this data 
> with the median income for each education level. A obviously 
> inneficient way to do this is
> 
> for ( k in 1: nrow(mydata) )            {
> l <- mydata$education[k]
> mydata$md[k] <- median(mydata$income[mydata$education==l],na.rm=T)
>                                                     }
> 
> Since mydata has nearly 30.000 rows, this will be done not 
> untill the end of this month. I thus need some help for 
> vectorizing this, please.
> 
> Thanks,
> 
> Dimitri
> 
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