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Re: Re: Fit with constraints?

• To: mathgroup at smc.vnet.net
• Subject: [mg23330] Re: [mg23316] Re: Fit with constraints?
• From: "Martin Rommel" <Martin_Rommel at mac.com>
• Date: Tue, 2 May 2000 00:43:12 -0400 (EDT)
• References: <200005012346.SAA27800@southpark.wolfram.com>
• Sender: owner-wri-mathgroup at wolfram.com

With hindsight it's obvious. Thanks for the tip. It should be in the book
maybe. I always knew that the Mathematica book is too brief.

Martin
----- Original Message -----
From: David Withoff <withoff at wolfram.com>
To: mathgroup at smc.vnet.net
Subject: [mg23330] Re: [mg23316] Re: Fit with constraints?


> Martin Rommel <Martin_Rommel at mac.com> wrote in message
> news:8eg5ee$giq at smc.vnet.net...
> > It seems the Fit function lacks the option to fix a point (like "set
> > intercept" in Excel).
> >
> > How is that best done?
> >
> > Martin
>
> Fixing a point or setting an intercept just means using a model
> that always passes through a particular point, as in
>
> In[1]:= Fit[{{1,2},{3,7},{4,6},{7,9},{11,14}}, x-4, x]
>
> Out[1]= 1.64706 (-4 + x)
>
> which fits the data to a straight line that passes through 4 (that is,
> it sets the y intercept to 4). If you have an example where you're
> not sure how to do this, you could try posting your example, or
> contacting technical support. In any case, fixing a point is just
> a simple modification of the model in the input to Fit.
>
> Dave Withoff
> Wolfram Research