[R] data.frame() size

[Matthew Dowle]

That explains it. Thanks. I don't need rownames though, as I'll only ever
use integer subscripts. Is there anyway to drop them, or even better not
create them in the first place? The memory saved (90%) by not having them
and 10 times speed up would be very useful. I think I need a data.frame
rather than a matrix because I have columns of different types in real life.

> rownames(d) = NULL
Error in "dimnames<-.data.frame"(`*tmp*`, value = list(NULL, c("a", "b" : 
        invalid 'dimnames' given for data frame


-----Original Message-----
From: pd at pubhealth.ku.dk [mailto:pd at pubhealth.ku.dk] On Behalf Of Peter
Dalgaard
Sent: 08 December 2005 18:57
To: Matthew Dowle
Cc: 'r-help at stat.math.ethz.ch'
Subject: Re: [R] data.frame() size


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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