DM41X Curve Fitting

Advantage Pac functions for statistical curve fitting.

CFIT program provides the functions to fit statistics data to LIN, Exp, LOG, Power and Best Fit

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• Save CFIT to a CST menu entry to make it easier to access

• Clear Statistics Registers with C (CLΣ)
• Enter Statistics in usual way with Y, ENTER, X, A(Σ+)
• Don't use any data points ≤0
• When all data pairs are entered press E (FIT)
• Now choose which type of fit to use
  • L = Linear
  • LOG = Logarithmic
  • Ex = Exponential
  • P = Power
  • B = Best Fit
• R/S to cycle through the coefficients of the curve fit a, b, R^2 (error ratio)
• You can next enter an x value to find the curve-fitted y value
• pressing R/S can exit back to the Curves menu L LOG Ex P B to try a different fit to the same data
• pressing R/S can exit back to the main menu to clear and enter a new set of data

• Linear y = a + bx
• Ex y = aebx
• Log y = a + b ln(x)
• Power y = a xb

• CFIT
• CLΣ
• 2.16 ENTER 0.72 A (Σ+)
• 1.61 ENTER 1.31 A (Σ+)
• 1.16 ENTER 1.95 A (Σ+)
• 0.85 ENTER 2.58 A (Σ+)
• 0.5 ENTER 3.14 A (Σ+)
• E (FIT)
• E (B) best fit
• display : LOG
• R/S
• display : a = 1.8515
• R/S
• display : b = -1.1021
• R/S
• display : r^2 = 0.9893
• R/S
• display : X=?
  • enter an X value if wanted, to get a y
  • 1.5 R/S
  • display : Y=1.4046
  • R/S
  • enter another, or press R/S again to exit to the curve fitting menu
• try a different curve fit…. (L, Ex etc) or
• R/S to exit to the top menu

the curve found is y = 1.8515 - 1.1021 ln(x)

— John Pumford-Green 31/07/24 14:46 BST