[R] reading a "sparse" matrix into R

Huntsinger, Reid reid_huntsinger at merck.com
Wed Apr 28 16:32:34 CEST 2004

I've used lists (generic vectors) for this, with integer storage mode. Then
I can easily manipulate them in R, they don't take too much room, and C code
to traverse them (e.g. find connected components) is fast.

Did you have a need for a data frame? That seems like it might be painful to

I read the text file with readLines.

Reid Huntsinger

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Aaron J. Mackey
Sent: Tuesday, April 27, 2004 5:10 PM
To: r-help at stat.math.ethz.ch
Subject: [R] reading a "sparse" matrix into R

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

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.



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