[R] changing names of vectors in list or data.frame

[Clint Harshaw]

When I combine separate vectors into one list, there are new names 
created. I'd like to change them to something more meaningful.

Here are two examples using data(zelazo) from library(ISwR):

 > library(ISwR)
 > data(zelazo)
 > attach(zelazo)
 > zelazo
$active
[1]  9.00  9.50  9.75 10.00 13.00  9.50

$passive
[1] 11.00 10.00 10.00 11.75 10.50 15.00

$none
[1] 11.50 12.00  9.00 11.50 13.25 13.00

$ctr.8w
[1] 13.25 11.50 12.00 13.50 11.50
 > walk <- stack(list("active"=active, "passive"=passive, "none"=none, 
"ctr.8w"=ctr.8w))
 > walk
    values     ind
1    9.00  active
[...rows deleted...]
23  11.50  ctr.8w

I want to name the first column "walking" and the second column 
"training". How do I do this?

Here is a second example:

 > walk2 <- data.frame(c(active, passive, none, ctr.8w), c(rep(1:4, 
c(length(active), length(passive), length(none), length(ctr.8w)))))
 > walk2
    c.active..passive..none..ctr.8w.
1                              9.00
[...rows deleted...]
23                            11.50
 
c.rep.1.4..c.length.active...length.passive...length.none...length.ctr.8w....
1 
        [...rows deleted...]
4
 >

The created names are very long. Again, I want the name of the first 
column to be "walking" and the second column to be "training".

Thanks,
Clint