Submitted by: Matt Dowle; Assigned to: Nobody; [R-Forge link](https://r-forge.r-project.org/tracker/index.php?func=detail&aid=2548&group_id=240&atid=978) To make the syntax easier (also if the expected key columns aren't present it can return earlier before starting to read the data) : http://stackoverflow.com/a/14952167/403310