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Topic: qr decomposition
Replies: 2   Last Post: Feb 8, 2011 12:15 PM

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DitzaN

Posts: 26
Registered: 6/2/09
qr decomposition
Posted: Feb 8, 2011 7:05 AM
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Hi,

I was using matlab 7.4(R2007a)
Now I am using matlab7.11 (R2007b)
I compared the results of qr function
the input was
-0.002567107834001 0.000011594153560 -0.001071830879080
-0.000348397823395 0.002671433293894 0.000451336098179
-0.000000757384596 -0.000000006341647 0.000000956196323
I didn't got the same answer in the two version
the difference between the version is
Q1-Q

ans =

0 -0.2690 -0.0000
0 1.9818 -0.0000
0 -0.0001 0.0000

R1-R

ans =

0 0 0
0 0.0053 0.0012
0 0 0

if I dividing them I got
Q1./Q

ans =

1.0000 -1.0000 1.0000
1.0000 -1.0000 1.0000
1.0000 -1.0000 1.0000

R1./R

ans =

1.0000 1.0000 1.0000
NaN -1.0000 -1.0000
NaN NaN 1.0000

why is this differences?
Is this decomposition is not unique?
Is there is way to get from 7.11 the same results as 7.4?

Thanks,
Ditza



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