Eigenvector mystery
10-18-2020, 09:31 PM (This post was last modified: 10-18-2020 09:40 PM by John Keith.)
Post: #1
 John Keith Senior Member Posts: 804 Joined: Dec 2013
Eigenvector mystery
I was just looking at the documentation for the Julia programming language today and I noticed something interesting.

In the second gray box on this page there is an example showing the calculation of eigenvectors and eigenvalues. I tried the same matrix on the HP 50 in approximate mode and the result for the eigenvectors was substantially different.

Wondering which set of eigenvectors was correct, I checked with Wolfram Alpha, which gave a third, completely different result! Going back to the 50g I tried the same matrix in exact mode, and obtained yet another result different from the previous 3. The eigenvalues in all 4 cases were the same however. The matrix is

Code:
 [[ -4  -17  [  2    2]]

Is this matrix so ill-conditioned that its eigenvectors can't be computed accurately? It doesn't seem so, its determinant is 26.
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 Messages In This Thread Eigenvector mystery - John Keith - 10-18-2020 09:31 PM RE: Eigenvector mystery - pinkman - 10-18-2020, 10:54 PM RE: Eigenvector mystery - JurgenRo - 10-19-2020, 06:33 PM RE: Eigenvector mystery - Albert Chan - 10-19-2020, 07:13 PM RE: Eigenvector mystery - Thomas Okken - 10-19-2020, 07:19 PM RE: Eigenvector mystery - JurgenRo - 10-19-2020, 07:35 PM RE: Eigenvector mystery - JurgenRo - 10-19-2020, 07:26 PM RE: Eigenvector mystery - pinkman - 10-19-2020, 08:57 PM RE: Eigenvector mystery - Thomas Okken - 10-19-2020, 09:42 PM RE: Eigenvector mystery - Valentin Albillo - 10-20-2020, 12:08 AM RE: Eigenvector mystery - JurgenRo - 10-21-2020, 06:57 PM RE: Eigenvector mystery - JurgenRo - 10-21-2020, 06:58 PM RE: Eigenvector mystery - Albert Chan - 10-18-2020, 11:58 PM RE: Eigenvector mystery - Michael de Estrada - 10-20-2020, 11:16 PM RE: Eigenvector mystery - John Keith - 10-24-2020, 02:03 PM RE: Eigenvector mystery - Albert Chan - 10-26-2020, 04:25 PM RE: Eigenvector mystery - John Keith - 10-27-2020, 12:37 PM