quadratic | R Documentation |
Computes orthogonal polynomials of degree 2 (Cohn and others, 1992). Used primarily in a linear regression formula.
quadratic(x, center = NULL)
x |
a numeric vector. Missing values are permitted and result in corresponding missing values in the output. |
center |
an optional value to use for the center of |
A matrix of two columns—the centered value of x
and its
square.
If center
is specified, then the polynomials will not
necessarily be orthogonal. If used in a linear regression formula, then the
coefficient of the linear term is the slope at center
.
The function quadratic
differs
from poly
in that the data are not scaled, so the regression
coefficients are directly interpretable in terms of the units of x
.
Cohn, T.A., Caulder, D.L., Gilroy, E.J., Zynjuk, L.D., and Summers, R.M., 1992, The validity of a simple statistical model for estimating fluvial constituent loads—An empirical study involving nutrient loads entering Chesapeake Bay: Water Resources Research, v. 28, no. 5, p. 937–942.
poly
## first and second orthogonal polynomials for the sequence from 1 to 10 quadratic(seq(10))
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.