[R] RAM usage

[Liaw, Andy]

> From: Vaidotas Zemlys [mailto:mpiktas at delfi.lt]
> Hi,
> 
>  >> I'm having problems while working with large data sets 
> with R 1.5.1 in
>  >> windows 2000. Given a integer matrix size of 30 columns 
> and  15000 rows
>  >> my function should return a boolean matrix size of about 
> 5000 rows and
>  >> 15000 columns.
> 
>  >That's  75million items of 4bytes each, hence almost 300Mb 
> for that one
>  >object.
> 
> Does that mean that R reserves 4 bytes for logical object 
> with length 1? On 
> the whole how much memory R allocates for different data 
> types? I searched 
> a bit, but I didn't find anything useful on this subject. I 
> would like to 
> know if it is possible how much memory R needs for storing 
> for example real 
> matrix size of 50 rows and 100 columns together with column 
> and row names. 
> Or where to find information on such subject.
> 
> I thought that R needs only 1 byte for storing logical byte, 
> and because of 
> that I underestimated the size of memory R would need to use.

You can use object.size() to get some idea on how R allocates memory:

> object.size(logical(1000))/1000
[1] 4.028
> object.size(integer(1000))/1000
[1] 4.028
> object.size(double(1000))/1000
[1] 8.028

So it seems like R allocates logicals as if they are integers.  My guess is
that this makes it easier to coerce logicals to integers for things like
sum(is.na(x))?

Andy


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