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[igraph] Trouble with arpack

From: David Morton
Subject: [igraph] Trouble with arpack
Date: Wed, 16 Apr 2008 18:17:47 +0200

I ran into trouble using arpack
with non-symmetric matrices. E.g.

  A <- matrix(runif(16,-1,1),4) 
  fct <- function(x,extra=NULL)A %*% x
  arpack(fct, options=list(n=ncol(A), nev=1, ncv=3), sym=FALSE)

generaly outputs eigenvectors that don't solve the aigenvalue equation Av=lv,
where l seems to correspond to the results obtained with eigen().
Is a full testing of arpack() planned in a near future?

Anyway, igraph is just a great piece of software!

David Morton de Lachapelle
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