memory management

zz <- data.frame(a=c(1,2,3),b=c(4,5,6))
zz

a b
1 1 4
2 2 5
3 3 6

a <- zz$a
a

[1] 1 2 3

a[2] <- 100
a

[1]   1 100   3

zz

a b
1 1 4
2 2 5
3 3 6

clearly a is a _copy_ of its namesake column in zz.

when was the copy made? when a was modified? at assignment?

is there a way to find out how much memory an object takes?

gc() appears not to reclaim all memory after rm() - anyone can confirm?

thanks!

Sam Steingold (http://sds.podval.org/) on Ubuntu 11.10 (oneiric) X 11.0.11004000
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