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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`.

`polyfit``     `Polynomial curve fitting
`polyvalm``    `Matrix polynomial evaluation