Re: performing least squares

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From: Tim Williams (saxifrax_at_pacbell*dot*net)
Date: 03/19/05 

Date: Sat, 19 Mar 2005 11:25:07 -0800

Darius,

If you want a "general" method then why not use solver? I've used this
in the past when fitting a dataset (assuming this is experimental
data) to one or more models. Works fine.

Tim

"Jay Somerset" <jay-1941-@hotmail.com> wrote in message
news:lr0n3114fbds3lsvotegva0fcklsh33lk7@4ax.com...
> On Thu, 17 Mar 2005 09:48:39 +0100, "Darius Blaszijk"
> <dhkblaszyjk@zeelandnet.nl> wrote:
>
>> Jay,
>>
>> What I meant was the following; y = a*x1^2 b*x1*x2. But in fact it
>> does not
>> matter as I need a general method.
>
> It certainly does matter. But if you have already decided that you
> don't
> need a definitive expression with coefficients, then no amount of
> advice is
> going to help you. Sad to say, it seems as though you do not
> understand
> least squares fits.
>
>>
>> Kind regards, Darius Blaszijk
>>
>>
>>
>>
>> "Jay Somerset" <jay-1941-@hotmail.com> schreef in bericht
>> news:r4mh31tg831nebd7rucdav6doma2vn33e7@4ax.com...
>> > On Thu, 17 Mar 2005 00:25:44 +0100, "Darius Blaszijk"
>> > <dhkblaszyjk@zeelandnet.nl> wrote:
>> >
>> > > Hello,
>> > >
>> > > I have the following data;
>> > >
>> > > y x1 x2
>> > > 12 1 10
>> > > 23 2 20
>> > > 34 3 30
>> > > 45 4 40
>> > > 56 5 50
>> > >
>> > >
>> > > And I would like to fit the following formula to this dataset;
>> > > "x1^2 +
>> x2 *
>> > > x1 = y"
>> > >
>> > > Can anybody give me a pointer on how to do this, preferebly
>> > > without
>> having
>> > > to linearize the dataset first? The "algorithm" proposed should
>> > > however
>> be
>> > > able to fit any formula / model to the dataset, eg be general
>> > > about
>> this.
>> > >
>> > > Kind regards, Darius Blaszijk
>> > >
>> >
>> > You seem to be missing something. You can't fit the formula as
>> > you wrote
>> it.
>> >
>> > What coefficients are you trying to determine? Do you really
>> > mean you
>> are
>> > trying to find "a" and "b" that best fit the equation y = a*x1^2
>> > b*x1*x2,
>> > or y= a*x1*(x1 + b*x2) or y= x1*(a*x1+b*x2), or something else?
>> >
>> > --
>> > Jay.
>> > (remove dashes for legal email address)
>>
>
> --
> Jay.
> (remove dashes for legal email address)

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