Re: Forcing a Fit through a Data Point (Mathematica 5)

• To: mathgroup at smc.vnet.net
• Subject: [mg43598] Re: Forcing a Fit through a Data Point (Mathematica 5)
• From: bobhanlon at aol.com (Bob Hanlon)
• Date: Tue, 23 Sep 2003 04:01:42 -0400 (EDT)
• References: <bkm7pa\$rhj\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```data={{0,0},{.5,.25},{1,.4},{1.5,.5},{2,.625},{2.5,.84615},{3,1},{3.5,
1.0588}};

To pass through the origin the form is y=a*x vice y=a*x+b.  Consequently,
remove the constant term from the target functions, i.e., use {x} vice {1, x}

abc = Fit[data, {x}, x]

0.324176 x

Needs["Graphics`Colors`"];

Plot[abc,{x,0,5},
PlotStyle->Green,
GridLines->Automatic,
AxesLabel->{"Time\n(sec)","  Change in\nDistance (cm)"},
Epilog->{Red,PointSize[0.02],Map[Point,data]},
ImageSize->400];

Bob Hanlon

In article <bkm7pa\$rhj\$1 at smc.vnet.net>, Hank Shih <airforce1 at comcast.net>
wrote:

<< I have a set of data for a experiment and I want to create
the best fit line. Based on the x-y coordinate system, I need the line
to go through (0, 0) no matter what. The data is as followed: data =
{{0,0}, {.5,.25}, {1,.4}, {1.5,.5}, {2,.625}, {2.5,.84615}, {3,1},
{3.5,1.0588}}.

data = {{0,0}, {.5,.25}, {1,.4}, {1.5,.5}, {2,.625}, {2.5,.84615},
{3,1}, {3.5,1.0588}}.

abc = Fit[data, {1, x, x}, x]
Plot[abc, {x, 0, 5}, GridLines -> Automatic, AxesLabel -> {"Time (in
sec)", "Change in Distance (in cm)"},
Epilog -> {PointSize[0.02], Map[Point, data]}]

Is there a easier way to do this through Mathematica 5? If not, how can
I force it through that (0, 0) point? >><BR><BR>

```

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