On Mar 18, 12:22�pm, dbd <d...@ieee.org> wrote:
> On Mar 18, 8:13�am, Dirk Bell <bellda2...@cox.net> wrote:
>
> > ...
>
> > Not really. Perhaps if you said what the data is you are talking
> > about you would answer the OP's question.
>
> > Dirk
>
> The answer to the OP's question is "yes" and the description of the
> calculation is in the first reference. The OP is welcome to ask for
> any further clarification desired.
>
> My remarks are in terms of the reference I gave (and the notation in):
> The normalized correlation calculated by fft as described in section 3
> on page 15 of:http://www.bksv.com/pdf/Bv0013.pdf
> Dual Channel FFT Analysis (Part I)
> Technical review No. 1 - 1984
>
> Usenet text does not provide a convenient substitute for math formulas
> that are available in references. I've taken the time to provide a
> price free accessible reference for that reason. And pointed to a
> particular section in the reference. Your previous responses led me to
> assume you were capable of accessing and reading the reference. If
> not, what kind of assistance in accessing the internet do you need?
>
> Dale B. Dalrymple
Dale,
I don't need any assistance, I am not the OP.
I think the OP needs to know how to compute the one normalization
factor function using FFTs.
Dirk
Reply by dbd●March 18, 20102010-03-18
On Mar 18, 8:13�am, Dirk Bell <bellda2...@cox.net> wrote:
> ...
>
> Not really. Perhaps if you said what the data is you are talking
> about you would answer the OP's question.
>
> Dirk
The answer to the OP's question is "yes" and the description of the
calculation is in the first reference. The OP is welcome to ask for
any further clarification desired.
My remarks are in terms of the reference I gave (and the notation in):
The normalized correlation calculated by fft as described in section 3
on page 15 of:
http://www.bksv.com/pdf/Bv0013.pdf
Dual Channel FFT Analysis (Part I)
Technical review No. 1 - 1984
Usenet text does not provide a convenient substitute for math formulas
that are available in references. I've taken the time to provide a
price free accessible reference for that reason. And pointed to a
particular section in the reference. Your previous responses led me to
assume you were capable of accessing and reading the reference. If
not, what kind of assistance in accessing the internet do you need?
Dale B. Dalrymple
Reply by Dirk Bell●March 18, 20102010-03-18
On Mar 17, 7:35�pm, dbd <d...@ieee.org> wrote:
> On Mar 17, 3:09�pm, Dirk Bell <bellda2...@cox.net> wrote:
> ...
>
> > Right. As both of us have noted, the definitions can be used. The
> > question of interest, I believe, is how to implement the calculation
> > with maximal use of FFTs, which means how to calculate the shift
> > dependent normalization factor with FFTs assuming it is efficient to
> > do so.
>
> > Dirk
>
> Will it help if I say "shift" the data through y instead of "slide"?
> There is no more to it than that. Calculate the FFT on time varying
> data in y at whatever strides (and thus, output sampling frequency)
> you wish to move through the data with.
>
> Dale B. Dalrymple
Not really. Perhaps if you said what the data is you are talking
about you would answer the OP's question.
Dirk
Reply by Dirk Bell●March 18, 20102010-03-18
On Mar 17, 7:35�pm, dbd <d...@ieee.org> wrote:
> On Mar 17, 3:09�pm, Dirk Bell <bellda2...@cox.net> wrote:
> ...
>
> > Right. As both of us have noted, the definitions can be used. The
> > question of interest, I believe, is how to implement the calculation
> > with maximal use of FFTs, which means how to calculate the shift
> > dependent normalization factor with FFTs assuming it is efficient to
> > do so.
>
> > Dirk
>
> Will it help if I say "shift" the data through y instead of "slide"?
> There is no more to it than that. Calculate the FFT on time varying
> data in y at whatever strides (and thus, output sampling frequency)
> you wish to move through the data with.
>
> Dale B. Dalrymple
No really. Perhaps if you said what the data was you were talking
about you would answer the OP's question.
Dirk
Reply by dbd●March 17, 20102010-03-17
On Mar 17, 3:09=A0pm, Dirk Bell <bellda2...@cox.net> wrote:
...
> Right. As both of us have noted, the definitions can be used. The
> question of interest, I believe, is how to implement the calculation
> with maximal use of FFTs, which means how to calculate the shift
> dependent normalization factor with FFTs assuming it is efficient to
> do so.
>
> Dirk
Will it help if I say "shift" the data through y instead of "slide"?
There is no more to it than that. Calculate the FFT on time varying
data in y at whatever strides (and thus, output sampling frequency)
you wish to move through the data with.
Dale B. Dalrymple
Reply by Dirk Bell●March 17, 20102010-03-17
On Mar 17, 2:24=A0pm, dbd <d...@ieee.org> wrote:
> On Mar 17, 7:05=A0am, Dirk Bell <bellda2...@cox.net> wrote:
>
>
>
>
>
> > On Mar 17, 2:47=A0am, dbd <d...@ieee.org> wrote:
>
> > > On Mar 16, 10:19=A0pm, Dirk Bell <bellda2...@cox.net> wrote:
> > > ...
>
> > > > Dale,
>
> > > > Interesting reference. =A0Using FFTs aren't they computing the freq=
uency
> > > > dependend coherence function rather than the normalized cross-
> > > > correlation?
>
> > > > Dirk
>
> > > Both are defined in the first reference.
> > > In the B&K formulation, the correlation coefficient is calculated fro=
m
> > > covariance and standard deviation coefficients. The coherence functio=
n
> > > is calculated from auto and cross spectrum functions.
>
> > > Dale B. Dalrymple
> > ...
> > I noticed both were defined I just didn't see the normalized cross
> > correlation computed with FFTs to the degree that it can be (ie.
> > including the normalization factor that is shift dependent).
>
> > Dirk
>
> B&K's instrument is a 2 channel real time analyzer. It is not set up
> to do any possible combination of x and y, but the definitions can be
> applied to any choices of x and y. Set x to your reference and slide
> data through y.
>
> Dale B. Dalrymple- Hide quoted text -
>
> - Show quoted text -
Right. As both of us have noted, the definitions can be used. The
question of interest, I believe, is how to implement the calculation
with maximal use of FFTs, which means how to calculate the shift
dependent normalization factor with FFTs assuming it is efficient to
do so.
Dirk
Reply by dbd●March 17, 20102010-03-17
On Mar 17, 7:05=A0am, Dirk Bell <bellda2...@cox.net> wrote:
> On Mar 17, 2:47=A0am, dbd <d...@ieee.org> wrote:
>
>
>
> > On Mar 16, 10:19=A0pm, Dirk Bell <bellda2...@cox.net> wrote:
> > ...
>
> > > Dale,
>
> > > Interesting reference. =A0Using FFTs aren't they computing the freque=
ncy
> > > dependend coherence function rather than the normalized cross-
> > > correlation?
>
> > > Dirk
>
> > Both are defined in the first reference.
> > In the B&K formulation, the correlation coefficient is calculated from
> > covariance and standard deviation coefficients. The coherence function
> > is calculated from auto and cross spectrum functions.
>
> > Dale B. Dalrymple
> ...
> I noticed both were defined I just didn't see the normalized cross
> correlation computed with FFTs to the degree that it can be (ie.
> including the normalization factor that is shift dependent).
>
> Dirk
B&K's instrument is a 2 channel real time analyzer. It is not set up
to do any possible combination of x and y, but the definitions can be
applied to any choices of x and y. Set x to your reference and slide
data through y.
Dale B. Dalrymple
Reply by Dirk Bell●March 17, 20102010-03-17
On Mar 17, 2:47=A0am, dbd <d...@ieee.org> wrote:
> On Mar 16, 10:19=A0pm, Dirk Bell <bellda2...@cox.net> wrote:
> ...
>
>
>
> > Dale,
>
> > Interesting reference. =A0Using FFTs aren't they computing the frequenc=
y
> > dependend coherence function rather than the normalized cross-
> > correlation?
>
> > Dirk
>
> Both are defined in the first reference.
> In the B&K formulation, the correlation coefficient is calculated from
> covariance and standard deviation coefficients. The coherence function
> is calculated from auto and cross spectrum functions.
>
> Dale B. Dalrymple
I noticed both were defined I just didn't see the normalized cross
correlation computed with FFTs to the degree that it can be (ie.
including the normalization factor that is shift dependent).
Dirk
Reply by Dirk Bell●March 17, 20102010-03-17
On Mar 17, 2:47=A0am, dbd <d...@ieee.org> wrote:
> On Mar 16, 10:19=A0pm, Dirk Bell <bellda2...@cox.net> wrote:
> ...
>
>
>
> > Dale,
>
> > Interesting reference. =A0Using FFTs aren't they computing the frequenc=
y
> > dependend coherence function rather than the normalized cross-
> > correlation?
>
> > Dirk
>
> Both are defined in the first reference.
> In the B&K formulation, the correlation coefficient is calculated from
> covariance and standard deviation coefficients. The coherence function
> is calculated from auto and cross spectrum functions.
>
> Dale B. Dalrymple
I noticed both were combined I just didn't see the normalized cross
correlation computed with FFTs to the degree that it can be (ie.
including the normalization factor that is shift dependent).
Dirk
Reply by dbd●March 17, 20102010-03-17
On Mar 16, 10:19=A0pm, Dirk Bell <bellda2...@cox.net> wrote:
...
>
> Dale,
>
> Interesting reference. =A0Using FFTs aren't they computing the frequency
> dependend coherence function rather than the normalized cross-
> correlation?
>
> Dirk
Both are defined in the first reference.
In the B&K formulation, the correlation coefficient is calculated from
covariance and standard deviation coefficients. The coherence function
is calculated from auto and cross spectrum functions.
Dale B. Dalrymple