[R] vectorization

[Huntsinger, Reid]

You can use tapply() to compute the medians, as in

meds <- tapply(mydata$inc,INDEX=mydata$ed,FUN=median)

then create a new column with the medians as

medianEd <- meds[mydata$ed]


Reid Huntsinger

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Dimitri Joe
Sent: Friday, June 17, 2005 1:01 PM
To: R-Help
Subject: [R] vectorization


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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