group by in R, ddply with weighted.mean

Question

I am trying to do a \"group by\" - style weighted mean in R. With some basic mean the following code (using the plyr package from Hadley) worked well.

ddply         


        

Answer 1

Use summarise (or summarize):

ddply(iris, "Species", summarise, 
  wmn = weighted.mean(Sepal.Length, Petal.Length),
  mn = mean(Sepal.Length))