[R] detecting singular matrices

[Murray Jorgensen]

My colleague runs R 1.7.1 under Windows XP. He remarks:

A
    [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9
b
[1] 1 2 3
solve(A,b)
[1] -0.3333333  0.6666667  0.0000000
solve(A)
           [,1]         [,2]        [,3]
[1,] -4.5036e+15  9.00720e+15 -4.5036e+15
[2,]  9.0072e+15 -1.80144e+16  9.0072e+15
[3,] -4.5036e+15  9.00720e+15 -4.5036e+15
eigen(A)
$values
[1]  1.611684e+01 -1.116844e+00 -1.303678e-15
with a condition number of  1.236260e+16 I think I'd like it to tell me it's singular like it used to :) and I know it is singular 
Under 1.6.0 also on XP I get

> solve(A,1:3)
Error in solve.default(A, 1:3) : singular matrix `a' in solve
> solve(A)
Error in solve.default(A) : singular matrix `a' in solve
> eigen(A)
$values
[1]  1.611684e+01 -1.116844e+00 -1.120190e-16
$vectors
           [,1]        [,2]       [,3]
[1,] -0.2719964 -0.76169140  0.3734378
[2,] -0.6159646 -0.08408654 -0.7468756
[3,] -0.9599328  0.59351831  0.3734378
Which seems to be preferable output.

Murray

--
Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
Department of Statistics, University of Waikato, Hamilton, New Zealand
Email: [EMAIL PROTECTED]                                Fax 7 838 4155
Phone  +64 7 838 4773 wk    +64 7 849 6486 home    Mobile 021 1395 862
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