Object not found error with ddply inside a function

Today's solution to this question is to make summarize into here(summarize). e.g.

myFunction <- function(x, y){    NewColName = "a"    z = ddply(x, y, here(summarize),            Ave = mean(eval(parse(text=NewColName)), na.rm=TRUE)    )    return(z)}

here(f), added to plyr in Dec 2012, captures the current context.

You can do this with a combination of do.call and call to construct the call in an environment where NewColName is still visible:

myFunction <- function(x,y){NewColName <- "a"z <- do.call("ddply",list(x, y, summarize, Ave = call("mean",as.symbol(NewColName),na.rm=TRUE)))return(z)}myFunction(d.f,sv)  b Ave1 0 1.52 1 3.5

I occasionally run into problems like this when combining ddply with summarize or transform or something and, not being smart enough to divine the ins and outs of navigating various environments I tend to side-step the issue by simply not using summarize and instead using my own anonymous function:

myFunction <- function(x, y){    NewColName <- "a"    z <- ddply(x, y, .fun = function(xx,col){                             c(Ave = mean(xx[,col],na.rm=TRUE))},                NewColName)    return(z)}myFunction(df,sv)

Obviously, there is a cost to doing this stuff 'manually', but it often avoids the headache of dealing with the evaluation issues that come from combining ddply and summarize. That's not to say, of course, that Hadley won't show up with a solution...