[R] more on apply on data frame

[Laura Holt]

Hi R People:

Several of you pointed out that using "tapply" on a data frame will work on 
the iris data frame.

I'm still having a problem.

The iris data frame has 150 rows, 5 variables.  The first 4 are numeric, 
while the last is a factor, which has the Species names.

I can use tapply for 1 variable at a time:
>tapply(iris[,1],iris[,5],mean)
    setosa versicolor  virginica
     5.006      5.936      6.588
>
but if I try to use this for all of the first 4, I get an error:
>tapply(iris[,1:4],iris[,5],mean)
Error in tapply(iris[, 1:4], iris[, 5], mean) :
        arguments must have same length
>
Any ideas of what I'm doing wrong, please?

Thanks,
Laura Holt
mailto: lauraholt_983 at hotmail.com
R Version 1.9.1
Windows