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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