### 21.5.3 Blackman window

The blackman_window command applies the Blackman window function to a sequence or its segment.

- blackman_window takes one mandatory argument and up to three optional arguments:
  - v, a real vector with length n.
  - Optionally, one of:
    - α, a real number (by default, α=0.16).
    - m,N ⟨,α⟩, a sequence of two integers and optionally a real number α (by default, m=0 and N=n).
- blackman_window returns the elementwise product of [vm,vm+1,…,vm+N−1] and the vector w of length N defined by

  wk= |
  1−α
  2
  | − |
  1
  2
  | cos | ⎛ ⎜ ⎜ ⎝ |
  2 k π
  N−1
  | ⎞ ⎟ ⎟ ⎠ | + |
  α
  2
  | cos | ⎛ ⎜ ⎜ ⎝ |
  4 k π
  N−1
  | ⎞ ⎟ ⎟ ⎠ | , k=0,1,…,N−1.

#### Example

listplot(blackman_window([1$1000]))