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colnames slow (PR#10470)

2 messages · tomas.larsson at gm.com, Uwe Ligges

Original
tomas.larsson at gm.com
# 
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.
user  system elapsed 
   9.98    0.00   10.00
user  system elapsed 
   0.01    0.00    0.02 

Sincerely,

Tomas
Uwe Ligges
#
tomas.larsson at gm.com wrote:
Documentation in the released version of R (2.6.1) tells us:

For a data frame, 'rownames'
      and 'colnames' are calls to 'row.names' and 'names' respectively,
      but the latter are preferred.

and on my machine I get:

system.time(names(x))
    user  system elapsed
       0       0       0


Uwe Ligges