User`s guide

Parametric Fitting
3-49
Fit the data using a fourth-degree Legendre polynomial with only even terms:
Because the Legendre polynomials depend only on the predictor variable and
constants, you use the Linear Equations pane on the Create Custom Equation
GUI. This pane is shown below for the model given by y
1
(x). Note that because
angle is given in radians, the argument of the Legendre terms is given by
cos(θ
α
).
y
1
x() a
0
a
2
1
2
---


3x
2
1–()a
4
1
8
---


35x
4
30x
2
3+–()++=
Create a custom linear equation
using even Legendre terms up
to fourth degree.
Specify a meaningful
equation name.