+2  A: 

Give

head(dataset)

and watch the name it has been given. Perhaps it would be something like:

dataset$data_transfer.Jingle.TCP.total_size_kb
gd047
Just beat me to it. `colnames(dataset)` would also work.
Richie Cotton
+1  A: 

Two ways:

dataset[["data_transfer.Jingle/TCP.total_size_kb"]]

or

dataset$`data_transfer.Jingle/TCP.total_size_kb`
Marek
This is really helpful if the variable name in the dataset really does have a forward slash (assigned in some way other than direct import).
Aniko