Branson, that's been on the wishlist for a while: https://r-forge.r-project.org/tracker/index.php?func=detail&aid=202&group_id=240&atid=978
It hasn't been an urgent enough need for anyone to dig into it. You can always use one data table to index a list. It may take more memory and a bit more bookkeeping for the user, but it's not that hard. - Tom On Fri, Sep 17, 2010 at 1:47 PM, Branson Owen <[email protected]> wrote: > I believe you have been already aware of what I know. Just add some > suggestions here. > > My understanding for data.frame is list of column VECTORs, so is > data.table. What I just learned is that data.frame now can be a list > of anything? > >> DF = data.frame(A = 1:3, B = rnorm(3)) >> DF$C = data.frame(a=1:3,b=rnorm(3)) >> DF$D = list(i=1:6, j = 1,k="?") >> print(DF) > > A B C.a C.b D > 1 1 -0.949565 1 -0.5815717 1, 2, 3, 4, 5, 6 > 2 2 -1.903233 2 -0.5087712 1 > 3 3 1.559566 3 1.4596933 ? > >> class(DF$C) > [1] "data.frame" > >> class(DF$D) > [1] "list" > > This is very cool to me! I can think of many benefits from this features. > > A very common example: if D is a function of B but with variable > output size, and I want to do fast grouping or sorting based on key A. > Before I know this, I would have to save them as separate objects and > add complexity of my codes. This just adds coding and management > sugar. No benefits to performance yet. > > But, I think data.table can make a difference just like it makes > differences to data.frame! There is no sorted / indexed list object > yet, right? If my variable-size outputs are millions length, any > aggregating operation on a less structured object like it will be > painful. Technically, data.table can make it a sorted list to enjoy > data.table high performance and syntax. > > I did some tests, use data.table as data.list, but most of the > syntaxes that work for data.frame doesn't work for data.table. > > I would expect this could be an easy feature, since data.frame is kind > of smoothly support it. Just a suggestion. *^^* > > Best regards, > _______________________________________________ > 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
