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lu_decomposition
2009 Feb 12
0
Sign differences amoung QR solutions.
...bit.gr/matrix-calculator/calculate.aspx I get:
R
-14.000 -21.000 14.000
0.000 -175.000 70.000
0.000 0.000 -35.000
Q
-0.857 0.394 0.331
-0.429 -0.903 -0.034
0.286 -0.171 0.943
Which seems to agree with the results of 'R'
This same matrix on http://en.wikipedia.org/wiki/QR_decomposition
R
14 -21 14
0 175 -70
0 0 35
Q
6/7 -69/175 -58/175
3/7 158/175 6/175
-2/7 6/36 -33/35
I have yet another algoithm that puts the R matrix as:
-14 -21 14
0 -175 70
0 0 35
And Q as:
Q:
-0.8571 0.3943 -0.3314
-0.4286 -0.9029 0.0343
0.2857 -0.1714 -0.9429
So Wikipedia shows different signs b...