Object not found error with ddply inside a function

Question

This has really challenged my ability to debug R code.

I want to use ddply() to apply the same functions to different columns that are sequentially nam

Answer 1

The problem lies in the code of the plyr package itself. In the summarize function, there is a line eval(substitute(...),.data,parent.frame()). It is well known that parent.frame() can do pretty funky and unexpected stuff. T

he solution of @James is a very nice workaround, but if I remember right @Hadley himself said before that the plyr package was not intended to be used within functions.

Sorry, I was wrong here. It is known though that for the moment, the plyr package gives problems in these situations.

Hence, I give you a base solution for the problem :

myFunction <- function(x, y){
    NewColName = "a"
    z = aggregate(x[NewColName],x[y],mean,na.rm=TRUE)
    return(z)
}
> myFunction(df,sv)
  b   a
1 0 1.5
2 1 3.5