Finding equation for regression curve

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SUMMARY

This discussion focuses on finding the equation for an interpolated function of any degree using tools like Mathematica, MATLAB, or Mathcad. The user highlights issues with Excel plots, where the displayed polynomial equation does not accurately reflect the data range, particularly with negative values for certain inputs. The conversation emphasizes the need for more precise methods for fitting regression curves and suggests using polynomial approximation algorithms for better accuracy in data representation.

PREREQUISITES
  • Familiarity with polynomial equations and their properties
  • Understanding of regression analysis techniques
  • Basic knowledge of Mathematica, MATLAB, or Mathcad
  • Experience with data plotting and interpretation
NEXT STEPS
  • Research "Polynomial Approximation algorithms" in MATLAB
  • Explore "Interpolation methods in Mathematica"
  • Learn about "Regression analysis techniques" in Mathcad
  • Investigate "Data visualization best practices" in Excel
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Data scientists, statisticians, and anyone involved in mathematical modeling or data analysis who seeks to improve the accuracy of regression curve fitting.

canadiangoose
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Homework Statement



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

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

How many data points do you have?
 
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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