Name columns within aggregate in R

You can use setNames as in:

blubb <- setNames(aggregate(dat$two ~ dat$one, ...), c("One", "Two"))

Alternatively, you can bypass the slick formula method, and use syntax like:

blubb <- aggregate(list(One = dat$one), list(Two = dat$two), ...)

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Update

This update is to just help get you started on deriving a solution on your own.

If you inspect the code for stats:::aggregate.formula, you'll see the following lines towards the end:

if (is.matrix(mf[[1L]])) {
    lhs <- as.data.frame(mf[[1L]])
    names(lhs) <- as.character(m[[2L]][[2L]])[-1L]
    aggregate.data.frame(lhs, mf[-1L], FUN = FUN, ...)
}
else aggregate.data.frame(mf[1L], mf[-1L], FUN = FUN, ...)

If all that you want to do is append the function name to the variable that was aggregated, perhaps you can change that to something like:

if (is.matrix(mf[[1L]])) {
  lhs <- as.data.frame(mf[[1L]])
  names(lhs) <- as.character(m[[2L]][[2L]])[-1L]
  myOut <- aggregate.data.frame(lhs, mf[-1L], FUN = FUN, ...)
  colnames(myOut) <- c(names(mf[-1L]), 
                       paste(names(lhs), deparse(substitute(FUN)), sep = "."))
}
else {
  myOut <- aggregate.data.frame(mf[1L], mf[-1L], FUN = FUN, ...)
  colnames(myOut) <- c(names(mf[-1L]), 
                       paste(strsplit(gsub("cbind\\(|\\)|\\s", "", 
                                           names(mf[1L])), ",")[[1]],
                             deparse(substitute(FUN)), sep = "."))
} 
myOut

This basically captures the value entered for FUN by using deparse(substitute(FUN)), so you can probably modify the function to accept a custom suffix, or perhaps even a vector of suffixes. This can probably be improved a bit with some work, but I'm not going to do it!

Here is a Gist with this concept applied, creating a function named "myAgg".

Here is some sample output of just the resulting column names:

> names(myAgg(weight ~ feed, data = chickwts, mean))
[1] "feed"        "weight.mean"
> names(myAgg(breaks ~ wool + tension, data = warpbreaks, sum))
[1] "wool"       "tension"    "breaks.sum"
> names(myAgg(weight ~ feed, data = chickwts, FUN = function(x) mean(x^2)))
[1] "feed"                         "weight.function(x) mean(x^2)"

Notice that only the aggregated variable name changes. But notice also that if you use a custom function, you'll end up with a really strange column name!

The answer to your first question is yes. You can certainly include the column names in the aggregate function. Using the names from your example above:

blubb <- aggregate(dat,list(One=dat$One,Two=dat$Two),sum)

I like the part about possibly pulling in the original column names automatically. If I figure it out I'll post it.