[R] reading a "sparse" matrix into R

[David Meyer]

Have you considered the read.matrix.csr() function in pkg. e1071? It
uses another sparse input format, but perhaps you can easily transform
your data in the supported one. Also, in my experience, data frames are
not the best basis for a sparse format since they might turn out to be
very memory consuming and slow... The sparse formats provided by the
SparseM package are better suited for this.

-d

Date: Tue, 27 Apr 2004 17:10:09 -0400
From: "Aaron J. Mackey" <amackey at pcbi.upenn.edu>
Subject: [R] reading a "sparse" matrix into R
To: r-help at stat.math.ethz.ch
Message-ID: <43D15D80-988F-11D8-A84D-000A958C5008 at pcbi.upenn.edu>
Content-Type: text/plain; charset=US-ASCII; format=flowed


I have a 47k x 47k adjacency matrix that is very sparse (at most 30 
entries per row); my textual representation therefore is simply an 
adjacency list of connections between nodes for each row, e.g.

node	connections
A		B	C	D	E
B		A	C	D
C		A	E
D		A
E		A	F
F		E
G
H

I'd like to import this into a dataframe of node/connection 
(character/vector-of-characters) pairs.  I've experimented with scan, 
but haven't been able to coax it to work.  I can also "hack" it with 
strsplit() myself, but I thought there might be a more elegant way.

Thanks,

-Aaron