Re: curve fitting
- To: mathgroup at smc.vnet.net
- Subject: [mg40820] Re: curve fitting
- From: bobhanlon at aol.com (Bob Hanlon)
- Date: Sat, 19 Apr 2003 23:02:47 -0400 (EDT)
- References: <b7qono$3in$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
data={{0,3.786392146},{15,3.81806915},
{30,3.880044496},{45,4.31622824},
{60,4.523878538},{90,4.900042894},
{120,5.175422767},{150,5.217956939},
{180,5.262434094},{240,5.377787989},
{300,5.36486329},{360,5.241879526},
{420,5.234405371},{480,5.228778272},
{540,5.219441168},{600,5.230700617},
{660,5.305355251},{720,5.41936145},
{780,5.50345499},{840,5.524101499},
{900,5.546731139},{960,5.498010869},
{1020,5.574792174},{1080,5.600864814},
{1140,5.589530789},{1200,5.537377461},
{1260,5.455131015},{1320,5.342847014},
{1380,5.344745156},{1440,5.344745156}};
xmin=Min[data[[All,1]]];
xmax=Max[data[[All,1]]];
To get straight line interpolation set the InterpolationOrder to one.
f=Interpolation[data, InterpolationOrder->1];
To include the origin, manually set the PlotRange
Plot[f[x],{x,xmin,xmax},PlotStyle->RGBColor[0,0,1],
Epilog->{AbsolutePointSize[5],RGBColor[1,0,0],
Point/@data},ImageSize->400, PlotRange->{0,6}];
Note that it skipped over a few points (second and third) because the number of
PlotPoints was too small. Increase the PlotPoints
Plot[f[x],{x,xmin,xmax},PlotStyle->RGBColor[0,0,1],
Epilog->{AbsolutePointSize[5],RGBColor[1,0,0],
Point/@data},ImageSize->400, PlotRange->{0,6},
PlotPoints->50];
However, if all you want is a plot of straight line interpolation you can use
ListPlot
ListPlot[data, PlotJoined->True,
PlotStyle->RGBColor[0,0,1],PlotRange->{0,6},
Epilog->{AbsolutePointSize[5],RGBColor[1,0,0],
Point/@data},ImageSize->400];
Bob Hanlon
In article <b7qono$3in$1 at smc.vnet.net>, <cbhat at purdue.edu> wrote:
<<
Subject: curve fitting
From: "C B" <cbhat at purdue.edu>
To: mathgroup at smc.vnet.net
Date: Sat, 19 Apr 2003 06:01:28 +0000 (UTC)
please look at the following mathematica code which I actually got from some
of the good people on this newsgroup. The plot obtained in the last line of
the code, does not really look exactly line the plot given by Microsoft
EXcel. Can anyone explain what they are different ? Is it possible to obtain
an interpolation function for the plot the way it appears in Excel?
Are there any ways in Mathematica of getting information about the errors in
the curve fitting?
data = {{0, 3.786392146}, {15, 3.81806915}, {30, 3.880044496}, {45,
4.31622824}, {60, 4.523878538}, {90, 4.900042894}, {120,
5.175422767}, {150, 5.217956939}, {180, 5.262434094}, {240,
5.377787989}, {300, 5.36486329}, {360, 5.241879526}, {420,
5.234405371}, {480, 5.228778272}, {540, 5.219441168}, {600,
5.230700617}, {660, 5.305355251}, {720, 5.41936145}, {780,
5.50345499}, {840, 5.524101499}, {900, 5.546731139}, {960,
5.498010869}, {1020, 5.574792174}, {1080, 5.600864814}, {1140,
5.589530789}, {1200, 5.537377461}, {1260, 5.455131015}, {1320,
5.342847014}, {1380, 5.344745156}, {1440, 5.344745156}}
<< NumericalMath`NIntegrateInterpolatingFunct`
f = Interpolation[data]
NIntegrateInterpolatingFunction[f[x], {x, 0, 1440}]
xmin = Min[data[[All, 1]]]
xmax = Max[data[[All, 1]]]
Plot[f[x], {x, xmin, xmax},
PlotStyle -> RGBColor[0, 0, 1],
Epilog -> {AbsolutePointSize[5],
RGBColor[1, 0, 0], Point /@ data},
ImageSize -> 400]
>><BR><BR>