[R] Binary Matrices

[Liaw, Andy]

> -----Original Message-----
> From: Uwe Ligges
> 
> Mark Edmondson-Jones wrote:
> 
> > I'm wanting to perform analysis (e.g. using eigen()) of 
> binary matrices - i.e. matrices comprising 0s and 1s.
> > 
> > For example:
> > 
> > n<-1000
> > test.mat<-matrix(round(runif(n^2)),n,n)
> > eigen(test.mat,only.values=T)
> > 
> > Is there a more efficient way of setting up test.mat, as 
> each cell only requires a binary digit?  I imagine R is 
> setting up a structure which could contain n^2 floats.
> 
> No. In principle you could use logicals,

... but that doesn't save any memory:

> object.size(integer(1e6))
[1] 4000028
> object.size(logical(1e6))
[1] 4000028

> but that does not help for further calculations in eigen().

Besides, if the problem size is really 1000 x 1000, one matrix in 
double precision is only 8MB.  As Reid said, if the matrix is sparse,
there's probably a lot more saving in both memory and computation
by using SparseM and Matrix packages.

Cheers,
Andy

 
> Uwe Ligges
> 
> 
> > Thanks in advance for any help.
> > 
> > Regards,
> > Mark
> > 
> > 
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