Re: [office] Re: [office-comment] Re: sigmoid curve fitting in trend lines

[robert_weir@us.ibm.com]

office@lists.oasis-open.org wrote on 10/26/2012 12:32:24
AM:

> From: "Andreas J. Guelzow" <andreas.guelzow@concordia.ab.ca>
> To: office@lists.oasis-open.org, 
> Date: 10/26/2012 12:32 AM
> Subject: Re: [office] Re: [office-comment] Re:
sigmoid curve fitting
> in trend lines
> Sent by: office@lists.oasis-open.org
> 
> On Thu, 2012-10-25 at 15:57 -0600, robert_weir@us.ibm.com wrote:
> > I'm not sure we want to specify the method used to fit the curve.
 We
> > should probably specify the outcome.   The specific algorithm
used
> > might vary according to the processor, number of processors,
etc. 
> > 
> > I'm sure Andreas would have some ideas, but I wonder if we could
say
> > something like, "Uses an implementation-defined method to
fit a
> > sigmoid curve to the data while minimizing the average squared
> > deviation".  Then we're specifying the outcome, but
allowing fo
> > innovation in the method.
> 
> 
> Are we sure that the proposals (and the calculation supposedly outlined
> in those papers I haven't read,) in fact create a curve that minimizes
> the average squared deviation?
> 
> I am not used to R, but looking at the example referenced in a previous
> message in this thread and considering R's SSlogis function it seems
to
> me that R's fitting depends not only on the data but also on three
> initial values. Are we sure that there is a unique sigmoid function
that
> can be fitted to a given set of data?
> 
> If there is more than one than a generic description as above will
not
> provide for interoperability.
> 

So what are our choices?

1) Say something in very general terms, like: "attempts
a 'best fit' of the data to the following model:" This allows implementations
to vary on the quality of the fit, but doesn't guarantee identical results.
 So similar to IRR().

2)Cite a specific algorithm, with the risk that it
might not be the best one today, or the best one 5 years from now.  But
it will give the same results to the extent everyone implements the cited
algorithm.

IIRC once you get beyond linear models, or ones that
can be transformed to linear models, you no longer generally have simple
techniques that easily yield the same answer.  You have optimization
heuristics that will depend not only on parameters of the mode, but also
parameters of the algorithm, like step size, number of iterations, etc.
 So although in theory we could do #2, wouldn't we be 2nd guessing
the implementor on a lot of these details?

-Rob

> Andreas
> 
> 
> > 
> > 
> > Patrick Durusau <patrick@durusau.net> wrote on 10/25/2012
05:26:46 PM:
> > 
> > > From: Patrick Durusau <patrick@durusau.net> 
> > > To: James Salsman <jsalsman@gmail.com>, 
> > > Cc: office-comment@lists.oasis-open.org 
> > > Date: 10/25/2012 05:26 PM 
> > > Subject: Re: [office-comment] Re: sigmoid curve fitting
in trend
> > lines 
> > > 
> > > James,
> > > 
> > > First, thanks for the references!
> > > 
> > > Second, standards can refer to other standards but generally
not to 
> > > periodical literature as normative.
> > > 
> > > Which means we will have to extract the necessary definitions
and 
> > > incorporate them in the text.
> > > 
> > > I will grab copies of them in the next day or so to see
what that
> > will take.
> > > 
> > > Hope you are having a great week!
> > > 
> > > Patrick
> > > 
> > > On 10/24/2012 09:43 PM, James Salsman wrote:
> > > > Patrick,
> > > >
> > > > Thank you for your question.
> > > >
> > > > First, please change "Gompertz sigmoid – Regression
with a
> > > > logistic...." to "Gompertz sigmoid – Regression
with a
> > Gompertz...."
> > > > on the fifth line of my original request below.  I'm
sorry about
> > that
> > > > typo, and I tried to fix it, but it apparently didn't
get fixed in
> > my
> > > > request.
> > > >
> > > > As for the methods of calculating the parameters for
fitting those
> > two
> > > > very important curves, instead of trying to describe
them, could
> > you
> > > > please reference these authoritative descriptions of
the
> > algorithms
> > > > instead?
> > > >
> > > > For logistic curve fitting: J. A. Nelder (March 1961)
"The Fitting
> > of
> > > > a Generalization of the Logistic Curve" _Biometrics_
vol. 17, no.
> > 1,
> > > > pp. 89-110: http://www.jstor.org/stable/2527498
> > > >
> > > > For Gompertz curve fitting: Karl W. Kaufmann (1981)
"Fitting and
> > using
> > > > growth curves" _Oecologia_ vol. 49, no. 3, pp.
293-299:
> > > > http://www.springerlink.com/content/w153v81q72400q62
> > > >
> > > > Please let me know if I can help any further.
> > > >
> > > > Best regards,
> > > > James Salsman
> > > >
> > > >
> > > > On Wed, Oct 24, 2012 at 3:28 PM, Patrick Durusau 
> > > <patrick@durusau.net> wrote:
> > > >> James,
> > > >>
> > > >> With regard to your request for the addition of:
> > > >>
> > > >>> "* logistic sigmoid – Regression with
a logistic sigmoid
> > function –
> > > >>> approximate the values of the series using
the model: y =
> > > >>> A+B/(1+e^(-(x-C)/D))
> > > >>>
> > > >>> "* Gompertz sigmoid – Regression with
a logistic sigmoid
> > function –
> > > >>> approximate the values of the series using
the model: y =
> > > >>> A+B·e^(C·e^(D·x))"
> > > >>
> > > >> To the ODF standard.
> > > >>
> > > >> Can you define the method for calculating the parameters
of these
> > two
> > > >> functions?
> > > >>
> > > >> Please pardon our delay in reaching your request.
> > > >>
> > > >> The TC has not made a decision about your request
but having the
> > additional
> > > >> information will make that task easier.
> > > >>
> > > >> Thanks!
> > > >>
> > > >> Hope you are having a great week!
> > > >>
> > > >> Patrick
> > > >>
> > > >> --
> > > >> Patrick Durusau
> > > >> patrick@durusau.net
> > > >> Former Chair, V1 - US TAG to JTC 1/SC 34
> > > >> Convener, JTC 1/SC 34/WG 3 (Topic Maps)
> > > >> Editor, OpenDocument Format TC (OASIS), Project
Editor ISO/IEC
> > 26300
> > > >> Co-Editor, ISO/IEC 13250-1, 13250-5 (Topic Maps)
> > > >>
> > > >> Another Word For It (blog): http://tm.durusau.net
> > > >> Homepage: http://www.durusau.net
> > > >> Twitter: patrickDurusau
> > > >>
> > > 
> > > -- 
> > > Patrick Durusau
> > > patrick@durusau.net
> > > Former Chair, V1 - US TAG to JTC 1/SC 34
> > > Convener, JTC 1/SC 34/WG 3 (Topic Maps)
> > > Editor, OpenDocument Format TC (OASIS), Project Editor ISO/IEC
26300
> > > Co-Editor, ISO/IEC 13250-1, 13250-5 (Topic Maps)
> > > 
> > > Another Word For It (blog): http://tm.durusau.net
> > > Homepage: http://www.durusau.net
> > > Twitter: patrickDurusau
> > > 
> > > 
> > > -- 
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> 
> -- 
> Andreas J. Guelzow, PhD, FTICA
> Concordia University College of Alberta
> [attachment "signature.asc" deleted by Robert Weir/Cambridge/IBM]