[R] averaging within columns

[Rau, Roland]

Hi, 

> I'm hoping there is something like
> 
> mean(dataname$wtime[name])
> 
> which will just create a column with length equal to the number of 
> different names (levels) and an average wtime for each.  So 
> far though, 
> I haven't had much luck figuring that one out.
> 

Does the following code do what you want?

#### given you have the data like this:
name <- c(rep("jo", 4), rep("tim",3), rep("ro", 2))
wtime <- c(1,2,1,3,3,2,2,1,2)
mydf <- data.frame(name=name, wtime=wtime)

#### this should give you the desired result
tapply(X=mydf$wtime, INDEX=list(mydf$name), FUN=mean)


Hope this turns out to be useful.

Best,
Roland


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