[R] data.frame() size

[Peter Dalgaard]

Matthew Dowle <mdowle at concordiafunds.com> writes:

> Hi,
> 
> In the example below why is d 10 times bigger than m, according to
> object.size ? It also takes around 10 times as long to create, which fits
> with object.size() being truthful.  gcinfo(TRUE) also indicates a great deal
> more garbage collector activity caused by data.frame() than matrix().
> 
> $ R --vanilla
> ....
> > nr = 1000000
> > system.time(m<<-matrix(integer(1), nrow=nr, ncol=2))
> [1] 0.22 0.01 0.23 0.00 0.00
> > system.time(d<<-data.frame(a=integer(nr), b=integer(nr)))
> [1] 2.81 0.20 3.01 0.00 0.00			# 10 times longer
> 
> > dim(m)
> [1] 1000000       2
> > dim(d)
> [1] 1000000       2				# same dimensions
> 
> > storage.mode(m)
> [1] "integer"
> > sapply(d, storage.mode)
>         a         b 
> "integer" "integer" 				# same storage.mode
> 
> > object.size(m)/1024^2
> [1] 7.629616
> > object.size(d)/1024^2
> [1] 76.29482					# but 10 times bigger
> 
> > sum(sapply(d, object.size))/1024^2
> [1] 7.629501					# or is it ?    If its not
> really 10 times bigger, why 10 times longer above ?

Row names!!


> r <- as.character(1:1e6)
> object.size(r)
[1] 72000056
> object.size(r)/1024^2
[1] 68.6646

'nuff said?

-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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