# plus

## Syntax

```C = plus(A, B, 'Tolerance', tolerance) C = A + B ```

## Description

Given two lag operator polynomials A(L) and B(L), ```C = plus(A, B, 'Tolerance', tolerance)``` performs a polynomial addition C(L) = A(L) + B(L)with tolerance `tolerance`. '`Tolerance`' is the nonnegative scalar tolerance used to determine which coefficients are included in the result. The default tolerance is `1e-12`. Specifying a tolerance greater than `0` allows the user to exclude polynomial lags with near-zero coefficients. A coefficient matrix of a given lag is excluded only if the magnitudes of all elements of the matrix are less than or equal to the specified tolerance.

`C = A + B` performs a polynomial addition.

If at least one of `A` or `B` is a lag operator polynomial object, the other can be a cell array of matrices (initial lag operator coefficients), or a single matrix (zero-degree lag operator).

## Examples

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Create two `LagOp` polynomials and add them:

```A = LagOp({1 -0.6 0.08}); B = LagOp({1 -0.5}); plus(A,B)```
```ans = 1-D Lag Operator Polynomial: ----------------------------- Coefficients: [2 -1.1 0.08] Lags: [0 1 2] Degree: 2 Dimension: 1 ```

## Algorithms

The addition operator (+) invokes plus, but the optional coefficient `tolerance` is available only by calling `plus` directly.