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polyfit -> polyval problem
From: |
Sergei Steshenko |
Subject: |
polyfit -> polyval problem |
Date: |
Wed, 22 Jun 2011 06:16:31 -0700 (PDT) |
Hello,
I can't figure out what I an doing wrong in the following example:
"
octave:42> [p, s, mu] = polyfit ((1:10)(:), 2 * (1:10)(:), 1);
octave:43> p
p =
6.0553 11.0000
octave:44> polyval(p, 1:10)
ans =
17.055 23.111 29.166 35.221 41.277 47.332 53.387 59.442
65.498 71.553
octave:45> s.yf
ans =
2.0000
4.0000
6.0000
8.0000
10.0000
12.0000
14.0000
16.0000
18.0000
20.0000
octave:46>
".
First of all, contents of 'p':
"
p =
6.0553 11.0000
"
do not make sense to. Because of the contents the result of reconstitution:
"
octave:44> polyval(p, 1:10)
ans =
17.055 23.111 29.166 35.221 41.277 47.332 53.387 59.442
65.498 71.553
".
doesn't make sense either.
But the 'yf' values are OK:
"
octave:45> s.yf
ans =
2.0000
4.0000
6.0000
8.0000
10.0000
12.0000
14.0000
16.0000
18.0000
20.0000
".
What am I missing here ?
It look like I can still use 'polyfit' (I need to fit a straight line) by
simply using the first and the last value of 'yf' to calculate 'k' and 'b'
for y = k * x + b .
Thanks,
Sergei.
- polyfit -> polyval problem,
Sergei Steshenko <=