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Fitter malfunctioning?

  1. #1
    Registered User
    Join Date
    08-01-2005
    Posts
    6

    Fitter malfunctioning?

    Hello--

    I attempted to plot a trendline as a new data set (I looked at the fit equation and created a new set of data with it). However, the line the equation draws is not the same as the trendline! Am I making a mistake somewhere?

    The black line is the trendline. The blue line is the line the equation describes.

    Thanks,
    Jennifer
    jenant@gmail.com

    For the Y column I'm using:
    =(0.0000000009*(J2^3)) - (0.000004*(J2^2)) + (0.0057*J2) + 0.3246

    Col J Col K
    X Y
    20 0.4370072
    30 0.4920243
    40 0.5462576
    50 0.5997125
    60 0.6523944
    70 0.7043087
    80 0.7554608
    90 0.8058561
    100 0.8555
    110 0.9043979
    120 0.9525552
    130 0.9999773
    140 1.0466696
    ...and so on...

    Output:
    http://general.krl.caltech.edu/~jenant/fitter.jpg

  2. #2
    Jon Peltier
    Guest

    Re: Fitter malfunctioning?

    Jennifer -

    Notice that the first two coefficients display only one significant
    digit each. This is plenty of room to introduce error into the fitted
    formula.

    Select the trendline formula, press the Ctrl-1 (numeral one) shortcut to
    the formatting dialog, and on the Number tab, choose a Scientific format
    with 15 digits. This will provide a much closer fit than your earlier
    attempt.

    - Jon
    -------
    Jon Peltier, Microsoft Excel MVP
    Peltier Technical Services
    Tutorials and Custom Solutions
    http://PeltierTech.com/
    _______


    itgoeson wrote:
    > Hello--
    >
    > I attempted to plot a trendline as a new data set (I looked at the fit
    > equation and created a new set of data with it). However, the line the
    > equation draws is not the same as the trendline! Am I making a mistake
    > somewhere?
    >
    > The black line is the trendline. The blue line is the line the
    > equation describes.
    >
    > Thanks,
    > Jennifer
    > jenant@gmail.com
    >
    > For the Y column I'm using:
    > =(0.0000000009*(J2^3)) - (0.000004*(J2^2)) + (0.0057*J2) + 0.3246
    >
    > Col J Col K
    > X Y
    > 20 0.4370072
    > 30 0.4920243
    > 40 0.5462576
    > 50 0.5997125
    > 60 0.6523944
    > 70 0.7043087
    > 80 0.7554608
    > 90 0.8058561
    > 100 0.8555
    > 110 0.9043979
    > 120 0.9525552
    > 130 0.9999773
    > 140 1.0466696
    > ..and so on...
    >
    > Output:
    > [image: http://general.krl.caltech.edu/~jenant/fitter.jpg]
    >
    >


  3. #3
    Registered User
    Join Date
    08-01-2005
    Posts
    6
    Ahhhh thank you!

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