# Blackman window function: blackman_window

### 15.2.15 Blackman window function: blackman_window

The blackman_window command finds a Blackman window of a sequence.

- blackman_window takes one mandatory argument and two optional arguments:
  - v, a real vector with length n.
  - Optionally, α, a real number (by default 0.16).
  - Optionally, an interval n0..n1 (by default 0..(n−1)).
- blackman_harris_window(v ⟨,α,n1..n2⟩) returns the elementwise product of [vn1,…,vn2] and the vector w of length N=n2−n1+1 defined by

  wk=

  1−α
  2

  −

  1
  2

  cos

  ⎛
  ⎜
  ⎜
  ⎝

  2 k π
  N−1

  ⎞
  ⎟
  ⎟
  ⎠

  +

  α
  2

  cos

  ⎛
  ⎜
  ⎜
  ⎝

  4 k π
  N−1

  ⎞
  ⎟
  ⎟
  ⎠

  for k=0,1,…,N−1.

#### Example.

Input:

L0:=randvector(1000,0..1):;
scatterplot(L0);

Output:

Input:

L:=blackman_window(L0):;
scatterplot(L);

Output: