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Math Help - Data Management-non-linear regression

  1. #1
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    Data Management-non-linear regression

    To get a best fine line (non-linear ones) for a scatter plot,
    what is the difference between a exponential curve and power regression curve?
    These 2 curves are tooooo similar, i just can't choose one among them to fit the scatter plot```
    can somebody give me an example or shapes of the scatter plots to distinguish them?
    thanks_for all your help.
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  2. #2
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    For a given regression on specific data:
    1) The Exponential will climb faster than the power in one direction.
    2) The Exponential levels off in the other direction.

    Over a very narrow Domain, they can be nearly indistinguishable. If you promise to stay in the very narrow Domain, it may not matter which you pick. If you attempt to extrapolate (outside the narrow Domain), you must be very, very careful.
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  3. #3
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    Quote Originally Posted by TKHunny View Post
    For a given regression on specific data:
    1) The Exponential will climb faster than the power in one direction.
    2) The Exponential levels off in the other direction.

    Over a very narrow Domain, they can be nearly indistinguishable. If you promise to stay in the very narrow Domain, it may not matter which you pick. If you attempt to extrapolate (outside the narrow Domain), you must be very, very careful.
    -yea .. i forget.. the power only for one side of the y axis
    usually i'll choose the exponential , cuz the curve looks better
    than you
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  4. #4
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    There is much to be said for "looks better", but it is even better to have some sort of idea before you start. If you have a theoretical basis for a power, rather than an exponential, please do not use the exponential, even if they appear to be indentical.

    Bad models can lead to bad results. Social consequences can be very ugly.
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  5. #5
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    i c...but i think my teacher won't care about that much, if the coefficient of determination is big enough_ he just say it's okay
    thanks again
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  6. #6
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    Granted. Nothing wrong with working within the parameters you have been given.

    Note: See, math isn't ALL about math. There's at least a little art and a little politics in there, too.
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