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Finding equation for regression curve

  1. Jan 24, 2009 #1
    1. The problem statement, all variables and given/known data

    I want to know how to find equation for the interpolated function of any degree. On Mathematica, for example.

    3. The attempt at a solution

    Unfortunately, on Excel, the plots are deceiving because the points on the plot are actually out of range.

    For example, this equation: - 0.037*Math.pow(i,5) + 0.857*Math.pow(i,4) - 8.406*Math.pow(i,3) + 32.33*Math.pow(i,2) - 46.68*i + 260.2

    is displayed to be in the range of 0 and 255 between values 1 and 21 for i.

    however, when plugging in numbers, values are clearly not in the range. you get a negative number for i =18.

    So therefore, is there a more accurate way of finding regression curves for data AND the equation for the curve?
  2. jcsd
  3. Jan 25, 2009 #2

    The Electrician

    User Avatar
    Gold Member

    Are you trying to fit a polynomial to your data, or can you fit other equations?

    How many data points do you have?
  4. Jan 25, 2009 #3
    use some software as Mathlab or Mathcad, find the algorythm for 'Polynomial Approxiamtion' and you will obtain approximating polynomial for given data (x and y values)
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