[Rd] eigen returns NAs from a real matrix

Spencer Graves spencer.graves at pdf.com
Sun Mar 18 06:23:17 CET 2007

Hi, All: 

      Attached please find a symmetric, indefinite matrix for which 
'eigen(...)$vectors' included NAs: 

 > load("eigenBug.Rdata")
 > sum(is.na(eigen(eigenBug)$vectors))
[1] 5670
 > sessioninfo()
Error: could not find function "sessioninfo"
 > sessionInfo()
R version 2.4.1 (2006-12-18)

LC_COLLATE=English_United States.1252;LC_CTYPE=English_United 
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] "stats"     "graphics"  "grDevices" "utils"     "datasets"  "methods" 
[7] "base"    

      Using EISPACK does NOT return NAs: 
 > sum(is.na(eigen(eigenBug, EISPACK=TRUE)$vectors))
[1] 0

      I traced the problem to the following line in 'eigen': 

            z <- if (!complex.x)
                .Call("La_rs", x, only.values, PACKAGE = "base")

      Best Wishes,
      Spencer Graves

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