polyval (MATLAB Function Reference)

Polynomial evaluation

Syntax

y = polyval(p,x)
[y,delta] = polyval(p,x,S)

Description

y = polyval(p,x)

returns the value of the polynomial p evaluated at x. Polynomial p is a vector whose elements are the coefficients of a polynomial in descending powers.

x can be a matrix or a vector. In either case, polyval evaluates p at each element of x.

[y,delta] = polyval(p,x,S)

uses the optional output structure S generated by polyfit to generate error estimates, y±delta. If the errors in the data input to polyfit are independent normal with constant variance, y±delta contains at least 50% of the predictions.

Remarks

The polyvalm(p,x) function, with x a matrix, evaluates the polynomial in a matrix sense. See polyvalm for more information.

Examples

The polynomial

is evaluated at x = 5, 7, and 9 with

p = [3 2 1];
polyval(p,[5 7 9])

which results in

ans =

    86   162   262

For another example, see polyfit.