Sending in Column Name to ddply from Function

Question

I'd like to be able to send in a column name to a call that I am making to ddply. An example ddply call:

ddply(myData, .(MyGrouping), summarise, count=sum(myColumnName))

If I have ddply wrapped within another function is it possible to wrap this so that I can pass in an arbitrary value as myColumnName to the calling function?

Answer 1

There has got to be a better way. And I couldn't figure out how to make it work with summarise.

my.fun <- function(df, count.column) { 
  ddply(df, .(x), function(d) sum(d[[count.column]]))
}

dat <- data.frame(x=letters[1:2], y=1:10)

> my.fun(dat, 'y')
  x V1
1 a 25
2 b 30
> 

Answer 2

As what @David Arenburg said, this question is pretty old. Today, either data.table or dplyr package can give you the same result with a much faster speed.

Here is the data.table version of the answer.

library(data.table)
my.fun <- function(myData, MyGrouping, myColumnName) { 
  setDT(myData)[, lapply(.SD, sum), by=MyGrouping, .SDcols=myColumnName]
}