# DECIMATE

The DECIMATE node is based on a numpy or scipy function. The description of that function is as follows: Downsample the signal after applying an anti-aliasing filter. By default, an order 8 Chebyshev type I filter is used. A 30 point FIR filter with Hamming window is used if ftype is 'fir'. Params: x : array_like The signal to be downsampled, as an N-dimensional array. q : int The downsampling factor. When using IIR downsampling, it is recommended to call decimate multiple times for downsampling factors higher than 13. n : int The order of the filter (1 less than the length for 'fir'). Defaults to 8 for 'iir' and 20 times the downsampling factor for 'fir'. ftype : str {'iir', 'fir'} or "dlti" instance If 'iir' or 'fir', specifies the type of lowpass filter. If an instance of an "dlti" object, uses that object to filter before downsampling. axis : int The axis along which to decimate. zero_phase : bool Prevent phase shift by filtering with 'filtfilt' instead of 'lfilter' when using an IIR filter, and shifting the outputs back by the filter's group delay when using an FIR filter. The default value of 'True' is recommended, since a phase shift is generally not desired. .. versionadded : : 0.18.0 Returns: out : DataContainer type 'ordered pair', 'scalar', or 'matrix'
Python Code
from flojoy import OrderedPair, flojoy, Matrix, Scalar
import numpy as np

import scipy.signal

@flojoy
def DECIMATE(
default: OrderedPair | Matrix,
q: int = 2,
n: int = 2,
ftype: str = "iir",
axis: int = -1,
zero_phase: bool = True,
) -> OrderedPair | Matrix | Scalar:
"""The DECIMATE node is based on a numpy or scipy function.

The description of that function is as follows:

Downsample the signal after applying an anti-aliasing filter.

By default, an order 8 Chebyshev type I filter is used. A 30 point FIR filter with Hamming window is used if ftype is 'fir'.

Parameters
----------
x : array_like
The signal to be downsampled, as an N-dimensional array.
q : int
The downsampling factor. When using IIR downsampling, it is recommended
to call decimate multiple times for downsampling factors higher than 13.
n : int, optional
The order of the filter (1 less than the length for 'fir').
Defaults to 8 for 'iir' and 20 times the downsampling factor for 'fir'.
ftype : str {'iir', 'fir'} or "dlti" instance, optional
If 'iir' or 'fir', specifies the type of lowpass filter.
If an instance of an "dlti" object, uses that object to filter before downsampling.
axis : int, optional
The axis along which to decimate.
zero_phase : bool, optional
Prevent phase shift by filtering with 'filtfilt' instead of 'lfilter'
when using an IIR filter, and shifting the outputs back by the filter's
group delay when using an FIR filter. The default value of 'True' is
recommended, since a phase shift is generally not desired.

Returns
-------
DataContainer
type 'ordered pair', 'scalar', or 'matrix'
"""

result = scipy.signal.decimate(
x=default.y,
q=q,
n=n,
ftype=ftype,
axis=axis,
zero_phase=zero_phase,
)

if isinstance(result, np.ndarray):
result = OrderedPair(x=default.x, y=result)
else:
assert isinstance(
result, np.number | float | int
), f"Expected np.number, float or int for result, got {type(result)}"
result = Scalar(c=float(result))

return result


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