DM41X PPC ROM Curve Fit

The PPC ROM's CV function does similar Curve Fitting to the Advantage Pac CFIT program, without the limitation on negative data point values.

Negative X values are acceptable for Linear and Exponential curves

Negative Y values are acceptable for Linear and Logarithmic

If any data point has BOTH X and Y negative then only Linear is possible.

XEQ ALPHACVALPHA

Unlike CFIT there is no displayed menu for the top-row buttons, so you need to remember the functions.

Unlike normal Stats entry (where Y-value is entered first, then ENTER, then X-value is entered second, so that the X-value is in the X register before pressing ∑+) here we enter in “conventional” order.

• Clear old data SHIFT E (Initialize)
• X ENTER Y Σ+
• X ENTER Y Σ+
• X ENTER Y Σ+
• X ENTER Y Σ+
• etc…..

once the data is accumulated either

• enter a fit-type digit (J)
  • 1 : Linear : Y = b*X + a
  • 2 : Exponential : Y = a*ebX
  • 3 : Logarithmic : Y = b*Ln(X) + a
  • 4 : Power : Y = a*Xb
• then press B to Solve Type J

or

• press E to Solve Best Type

The solution appears as

Z : r correlation coefficient Y : a coefficient X : b coefficient

You can now get estimates of Y (for a given X) or X (for a given Y)

You can accumulate more data (to add to what's already there) and do another FIT calculation.

If you want equally spaced X coordinates for single variable Y-data CV puts incrementing digit in X so you simply

ENTER Y1 Σ+

ENTER Y2 Σ+

ENTER Y3 Σ+

ENTER Y4 Σ+

…

and you accumulate as if you'd entered (1,Y1), (2,Y2), (3,Y3), (4,Y4)…

If you have X and Y data then the automatically incrementing X is overwritten by the manually entered real X values.

Negative X and Y values allowed for a Linear Fit

• SHIFT E Initialize
• 1.5CHS ENTER 3CHS ∑+
• 1.1ENTER 5.2 ∑+
• 4.5ENTER 12.6 ∑+
• 8ENTER 20 ∑+
• 10ENTER 23 ∑+
• 15.6ENTER 34 ∑+

• 1 (for Linear Fit J = 1) B

• Z : 0.995734680 : r correlation coefficient
• Y : 2.017167182 : a coefficient (y-intercept)
• X : 2.113978698 : b coefficient (gradient)

Linear Equation : Y = 2.114 X + 2.017

Predict Y for X = 20

• 20 C
  • 44.9674114

Predict X for Y = 25

• 25 D
  • 10.87183747

See also : DM41X PPC ROM Solve & Integrate

Page created : 16/02/26 20:13 GMT

Page updated : 17/02/26 08:00 GMT