MATLAB Function Reference
polyval

Polynomial evaluation

Syntax

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

Description

```y = polyval(p,x) ``` returns the value of a polynomial of degree `n` evaluated at `x`. The input argument `p` is a vector of length `n+1` whose elements are the coefficients in descending powers of the polynomial to be evaluated.

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

```y = polyval(p,x,[],mu) ``` uses in place of . In this equation, and . The centering and scaling parameters `mu = ` are optional output computed by `polyfit`.

```[y,delta] = polyval(p,x,S) and [y,delta] = polyval(p,x,S,mu) ``` use 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 = 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`.

`polyfit`, `polyvalm`