polydeg function

Degree of Polynomial Determination

Tests for the degree of a polnomial. This test was suggested by Graybill (1976) and is discussed from a robust point-of-view in Section 4.7.1. of Kloke and McKean (2014)/4.6.1 of Kloke and McKean (2024).

polydeg(y, x, P, alpha = 0.05)

Arguments

• y: vector of responses
• x: Predictor
• P: Super degree of polynomial which provides a satisfactory fit
• alpha: Level of the testing

Details

Returns the degree of the polynomial based on the algorithm.

Returns

• deg: The determined degree

• coll: Matrix of step information

• fitf: Fit of the polynomial based on the determoned degreer

References

Graybill, F.A. (1976), Theory and application of the linear model, North Scituate, Ma: Duxbury Press.

Kloke, J. and McKean, J.W. (2014), Nonparametric statistcal methods using R, Boca Raton, FL: Chapman-Hall. Kloke, J. and McKean, J.W. (2024), Nonparametric statistcal methods using R, Second Edition, Boca Raton, FL: Chapman-Hall.

Examples

x <- 1:20
 xc <- x - mean(x)
 y<- .2*xc + xc^3 +rt(20,3)*90
 plot(y~x)
 polydeg(y,xc,6)