Hi,
There's no technical reason. I guess enough people realise now that the
set* functions change the object by reference. So if setnames worked on
data.frame :
DF1 = data.frame(a=1:3, b=4:6)
DF2 = DF1
setnames(DF2, "b", "B")
This would change both DF1 and DF2. There might be someone who throws
up their hands in horror and says this breaks everything they've known
about data.frame, too. Isn't it enough that data.table breaks everything
already?
We'd have to take a deep breath and calmly explain copy() is needed :
DF1 = data.frame(a=1:3, b=4:6)
DF2 = copy(DF1)
setnames(DF2, "b", "B")
So the reason setnames() hasn't so far been enabled for data.frame is
just for safety (using it on a data.frame accidentally) and to avoid
complaints and negative Twitterers. On the other hand setnames
(different from setNames) is a data.table function so it's not like
we're overloading <- or anything.
I suppose setnames() could copy the whole DF2 just like base. But that
defeats it's purpose, set* functions work by reference. setnames() is a
little different in that it's more convenient and safer than base
syntax, too, though; e.g., changing a column name by name. So I can see
someone might want to use it for that reason alone and not mind it
copies the whole DF when passed a DF.
Matt
On 01/10/13 20:51, Ricardo Saporta wrote:
Hi All,
I'm wondering if there are any potential problems or unforseen
pitfalls with having
setnames(x, nms)
call
setattr(x, "names", nms)
when x is not a data.table.
Thoughts?
Rick
Ricardo Saporta
Graduate Student, Data Analytics
Rutgers University, New Jersey
e: [email protected] <mailto:[email protected]>
_______________________________________________
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
