eigenvalues issue - simple interpretation error?



>>>>> "Evan" == Evan Cooch <evan.cooch at cornell.edu> writes:

    Evan> Consider
    Evan> test : matrix([-0.13333333333333,-0.16666666666667],[0.04,0.0]);
    Evan> when I execute
    Evan> float(eigenvalues(test));
    Evan> I get
    Evan> (%o210) [[-4.971296243246757*10^-28*(9.4825272469217148*10^25*%i+1.3410318638167688*10^26),
    Evan> 4.971296243246757*10^-28*(9.4825272469217148*10^25*%i-1.3410318638167688*10^26)],[1.0,1.0]]
    Evan> However, I *know* the eigenvalues for this matrix are
    Evan> -.6666666665e-1+.4714045212e-1*I, -.6666666665e-1-.4714045212e-1*I
    Evan> (These are what Maple, Mathematica, and R all return, in some fashion).
    Evan> So, either Maxima is in error, or I'm not interpreting the output correctly. At minimum, I need to


As an alternative to what Rupert gave, you can try dgeev.  First,
load(lapack), which might take a while as it compiles everything.
Then

dgeev(test);
[[.04714045207910694 %i - .06666666666666499, 
                   - .04714045207910694 %i - .06666666666666499],
                     false, false]

Use ? dgeev to understand what's returned, but basically the first
item in the list above is a list of the eigenvalues that you were
looking for.

Ray