colnames slow (PR#10470)

Full_Name: Tomas Larsson
Version: 2.6.0
OS: Windows XP
Submission from: (NULL) (198.208.251.24)


This is not a bug, it is a performance issue but I think it should have an easy
fix.

I have a large matrix (about 2,000,000 by 20), when I type colnames(x) it takes
a long time to get the result.  However, if I select just the first couple of
rows of the matrix I don't have to wait for the result. See below for example.

system.time(colnames(x))

user  system elapsed 
   9.98    0.00   10.00

system.time(colnames(x[1:2,]))

user  system elapsed 
   0.01    0.00    0.02 

Sincerely,

Tomas