minor fix to remove partial matching which warns in R 3.1.0 (#3415)
minor fix to remove partial matching which warns in R 3.1.0 (#3415)


Rdatatable/data.table,Rdatatable/data.table,Rdatatable/data.table,vlulla/data.table,vlulla/data.table,vlulla/data.table,vlulla/data.table,jangorecki/data.table,jangorecki/data.table,jangorecki/data.table,jangorecki/data.table,Rdatatable/data.table