# filter2

Perform 2D FIR filtering.

## Syntax

y = filter2(b,x)

y = filter2(...,shape)

## Inputs

`b`- The 2D polynomial coefficients of the FIR filter.
`x`- The 2D data to be filtered.
`shape`- Options include:

## Outputs

- y
- The filtered 2D data.

## Example

```
b = [5,4,3;4,3,2;3,2,1];
y = filter2(b,[1,2,3,4,5;2,3,4,5,6;3,4,5,6,7;4,5,6,7,8])
```

```
y = [Matrix] 4 x 5
14 32 47 62 58
32 69 96 123 110
47 96 123 150 131
46 89 110 131 110
```

## Comments

filter2(b,x) is similar to conv2(x,y), except that the rows and columns
of b are reversed compared to y, and the two functions do not use the
same default for `shape`.