Aggregate and Weighted Mean in R

Question

I\'m trying to calculate asset-weighted returns by asset class. For the life of me, I can\'t figure out how to do it using the aggregate command.

My data frame look

Answer 1

This is also easily done with aggregate. It helps to remember alternate equations for a weighted mean.

rw <- dat$return * dat$assets
dat1 <- aggregate(rw ~ assetclass, data = dat, sum)
datw <- aggregate(assets ~ assetclass, data = dat, sum)
dat1$weighted.return <- dat1$rw / datw$assets