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Modelling an Exponential Curve

  1. Aug 23, 2011 #1
    Hi guys,

    I need to model a curve and I am trying to come up with an exponential equation. I have several points I can work with and this is what I tried so far. (I want to know if this is the correct method or if there is a more precise way to go about this)

    I am working on something of the format: a*bt

    My first point in the graph will be when t = 0, hence, I presume the best pick for my value of a would be my first y coordinate point in the graph: 554.8

    My doubt arises from this point on:

    When I have 554.8*bt should I set up a pair or simultaneous equations or can I say that b is equal to the "rate of growth of my graph"? That is, if my y coordinate points are 609, 657.5 my rate of growth would be (657.5/609)

    Since my graph is not a perfect exponential fit I was thinking of adding a constant:

    a*bct

    But that's something different.

    Thanks,
    ProPM
     
  2. jcsd
  3. Aug 23, 2011 #2

    hotvette

    User Avatar
    Homework Helper

    I'd probably use y = aebt and use two points to determine a and b. A trick is to take the natural log of both sides so you end up with a linear equation. A more elaborate method (if the points have noise and don't fit a curve perfectly) would be a least squares approach, but that's much more involved (especially in the category of precalculus).
     
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