Looks like the c(x)[...] bit used to be as.matrix(x)[...]. Not sure
why the change was made many years ago, but this was before names were
handled explicitly. It would definitely be better to not force the
duplicate, at least in the case where we are sure c() and [ would not
dispatch.
Best,
luke
On Mon, 4 May 2015, peter dalgaard wrote:
On 04 May 2015, at 19:59 , franknarf <by.hook...@gmail.com> wrote:
But I'm still wondering why diag() uses c()...? With it being so slow, I'd
be inclined to write a qdiag() without the c() and just use that the next
time I need matrix algebra. Any insight would be appreciated; thanks!
Well, there are two possibilities: Either it is deliberate or it isn't.
The latter isn't too unlikely, given that the effect is seen for large
matrices. I would appear to be a matter of O(n) (picking out n items) vs.
O(n^2) (copying an n x n matrix), but this might drown out in a context
involving matrix multiplication and/or inversion, both of which are O(n^3).
If it is deliberate, the question is why. There could be devils in the details;
notice in particular that c() strips off non-name attributes. However, I'm not
aware of a situation where such attributes could cause trouble.
-pd
--
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
