+1 on exporting setDF On Mon, Apr 7, 2014 at 11:25 AM, Arunkumar Srinivasan <[email protected]> wrote: > as.data.frame is a S3 with .data.table method and is definitely faster than > data.frame(). But it still does copy(.). data.frame(.) would also convert > strings to factors by default (if stringsAsFactors=TRUE). > > The most efficient way to convert data.table to data.frame would be to do > things by reference (in place). The code is already available in > as.data.frame, just remove the copy(.): > > # convert data.table to data.frame by reference > setDF <- function(x) { > if (!is.data.table(x)) > stop("x must be a data.table") > setattr(x, "row.names", .set_row_names(nrow(x))) > setattr(x, "class", "data.frame") > setattr(x, "sorted", NULL) > setattr(x, ".internal.selfref", NULL) > } > > Now you've a function that'll convert a data.table to data.frame by > reference. > > require(data.table) > dat <- data.table(x=1:5, y=6:10) > setDF(dat) # dat is now a data.frame > > Probably we should export this function as well, like setDT so that users > can switch between the two as they desire without hitting performance? > > > Arun > > From: Chris Neff [email protected] > Reply: Chris Neff [email protected] > Date: April 7, 2014 at 5:32:47 PM > To: [email protected] > [email protected] > Subject: [datatable-help] Is there any overhead to converting back and > forth from a data.table to a data.frame? > > I prefer data.tables for all the code processing I do. But others on my > team using my functions aren't comfortable with data.tables, so most of the > libraries I write end with > > return(data.frame(DT)) > > Is there any copying or other overhead happening there? Since it inherits > from data.frame, I think the answer is no. > > Now, if I have a function that does such a return, but I wrap that itself in > a data.table call: > > data.table(func_that_returns_df()) > > Is there any inefficiency there? Is there a difference between data.table() > and as.data.table() here? > _______________________________________________ > datatable-help mailing list > [email protected] > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > > > _______________________________________________ > datatable-help mailing list > [email protected] > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
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