# tensorplay.signal.windows.general_cosine

Source: https://www.tensorplay.cn/docs/generated/tensorplay.signal.windows.general_cosine.html

```python
tensorplay.signal.windows.general_cosine(M, *, a: Iterable, sym: bool = True, dtype: dtype | None = None, layout: Layout = tensorplay.strided, device: device | None = None, requires_grad: bool = False) → Tensor
```

Computes the general cosine window, a weighted sum of cosines whose
frequencies are integer multiples of the fundamental.

The samples are

$$w_n = \sum^{M-1}_{i=0} (-1)^i a_i \cos{ \left( \frac{2 \pi i n}{M - 1}\right)}$$

The window is scaled so that its largest value is 1. The value 1 itself does not occur when M is even and sym is True.

Parameters:

M ([int](https://docs.python.org/3/builtins/functions.html#int)) – number of points of the returned window.

Keyword Arguments:

- a (Iterable) – coefficient of each cosine term.

- sym ([bool](https://docs.python.org/3/builtins/functions.html#bool), optional) – if False, returns a periodic window, which is the usual choice for spectral analysis. If True, returns a symmetric window, which is the usual choice for filter design. Default: True.

- dtype ([tensorplay.dtype](/docs/generated/tensorplay.DType.html#tensorplay.DType), optional) – the desired data type of the returned tensor. Default: if None, uses the global default (see [tensorplay.set_default_dtype()](/docs/generated/tensorplay.set_default_dtype.html#tensorplay.set_default_dtype)).

- layout ([tensorplay.Layout](/docs/generated/tensorplay.Layout.html#tensorplay.Layout), optional) – the desired layout of the returned tensor. Default: tensorplay.strided.

- device ([tensorplay.device](/docs/generated/tensorplay.Device.html#tensorplay.Device), optional) – the desired device of the returned tensor. Default: if None, uses the current default tensor device (see [tensorplay.set_default_device()](/docs/generated/tensorplay.set_default_device.html#tensorplay.set_default_device)).

- requires_grad ([bool](https://docs.python.org/3/builtins/functions.html#bool), optional) – whether autograd should record operations on the returned tensor. Default: False.

Examples:

```
>>> # Symmetric general cosine window with 3 coefficients.
>>> tensorplay.signal.windows.general_cosine(10, a=[0.46, 0.23, 0.31], sym=True)
tensor([0.54, 0.3376, 0.1288, 0.42, 0.9136, 0.9136, 0.42, 0.1288, 0.3376, 0.54])

>>> # Periodic general cosine window with 2 coefficients.
>>> tensorplay.signal.windows.general_cosine(10, a=[0.5, 1 - 0.5], sym=False)
tensor([0., 0.0955, 0.3455, 0.6545, 0.9045, 1., 0.9045, 0.6545, 0.3455, 0.0955])
```