Convert a data frame to a data.table without copy

Question

I have a large data frame (in the order of several GB) that I\'d like to convert to a data.table. Using as.data.table creates a copy of the data fr

Answer 1

This is available from v1.9.0+. From NEWS:

o Following this S.O. post, a function setDT is now implemented that takes a list (named and/or unnamed), data.frame (or data.table) as input and returns the same object as a data.table by reference (without any copy). See ?setDT examples for more.

This is in accordance with data.table naming convention - all set* functions modifies by reference. := is the only other that also modifies by reference.

require(data.table) # v1.9.0+
setDT(data) # converts data which is a data.frame to data.table *by reference*

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