On Jan 3, 2010, at 10:46 PM, david hilton shanabrook wrote:
I want to use aggregate with the mean function on specific columns
gender <- factor(c("m", "m", "f", "f", "m"))
student <- c(0001, 0002, 0003, 0003, 0001)
score <- c(50, 60, 70, 65, 60)
basicSub <- data.frame(student, gender, score)
basicSubMean <- aggregate(basicSub, by=list(basicSub$student),
FUN=mean, na.rm=TRUE)
> basicSubMean <- aggregate(basicSub$score, by=list(basicSub
$student), FUN=mean, na.rm=TRUE)
> basicSubMean
Group.1 x
1 1 55.0
2 2 60.0
3 3 67.5
This doesn't work, one cannot take the mean of a factor (gender).
Is there any way of specifying which columns to use for the mean? I
want to aggregate by student, obtaining mean scores, and assume any
other factors are unchanging in a specific student, ie. gender.
Thanks
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--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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