## Syntax

```Y = dyaddown(X,EVENODD) Y = dyaddown(X) Y = dyaddown(X,EVENODD,'type') Y = dyaddown(X,'type',EVENODD) Y = dyaddown(X) Y = dyaddown(X,'type') Y = dyaddown(X,0,'type') Y = dyaddown(X,EVENODD) Y = dyaddown(X,EVENODD,'c') ```

## Description

`Y = dyaddown(X,EVENODD)` where `X` is a vector, returns a version of `X` that has been downsampled by 2. Whether `Y` contains the even- or odd-indexed samples of `X` depends on the value of positive integer `EVENODD`:

• If `EVENODD` is even, then ```Y(k) = X(2k)```.

• If `EVENODD` is odd,   then `Y(k) = X(2k+1)`.

`Y = dyaddown(X)` is equivalent to ```Y = dyaddown(X,0)``` (even-indexed samples).

`Y = dyaddown(X,EVENODD,'type')` or ```Y = dyaddown(X,'type',EVENODD)```, where `X` is a matrix, returns a version of `X` obtained by suppressing one out of two:

 Columns of `X` If `'type'``= 'c'` Rows of `X` If `'type'``= 'r'` Rows and columns of `X` If `'type'``= 'm'`

according to the parameter `EVENODD`, which is as above.

If you omit the `EVENODD` or `'type'` arguments, `dyaddown` defaults to `EVENODD = 0` (even-indexed samples) and `'type'``= 'c'` (columns).

`Y = dyaddown(X)` is equivalent to ```Y = dyaddown(X,0,'c')```.
`Y = dyaddown(X,'type')` is equivalent to `Y = dyaddown(X,0,'type')`.
`Y = dyaddown(X,EVENODD)` is equivalent to `Y = dyaddown(X,EVENODD,'c')`.

## Examples

```% For a vector. s = 1:10 s = 1 2 3 4 5 6 7 8 9 10 dse = dyaddown(s) % Downsample elements with even indices. dse = 2 4 6 8 10 % or equivalently dse = dyaddown(s,0) dse = 2 4 6 8 10 dso = dyaddown(s,1) % Downsample elements with odd indices. dso = 1 3 5 7 9 % For a matrix. s = (1:3)'*(1:4) s = 1 2 3 4 2 4 6 8 3 6 9 12 dec = dyaddown(s,0,'c') % Downsample columns with even indices. dec = 2 4 4 8 6 12 der = dyaddown(s,1,'r') % Downsample rows with odd indices. der = 1 2 3 4 3 6 9 12 dem = dyaddown(s,1,'m') % Downsample rows and columns % with odd indices. dem = 1 3 3 9 ```

## References

Strang, G.; T. Nguyen (1996), Wavelets and Filter Banks, Wellesley-Cambridge Press.

## Extended Capabilities 