LowpassFilter

LowpassFilter[data,ωc]

applies a lowpass filter with a cutoff frequency ωc to an array of data.

LowpassFilter[data,ωc,n]

uses a filter kernel of length n.

LowpassFilter[data,ωc,n,wfun]

applies a smoothing window wfun to the filter kernel.

Details and Options

  • LowpassFilter is commonly used to locally smooth data, with the amount of smoothing dependent on the value of the cutoff frequency ωc. Smaller values of ωc result in greater smoothing.
  • The data can be any of the following:
  • listarbitrary-rank numerical array
    tseriestemporal data such as TimeSeries and TemporalData
    imagearbitrary Image or Image3D object
    audioan Audio or Sound object
  • When applied to images and multidimensional arrays, filtering is applied successively to each dimension, starting at level 1. LowpassFilter[data,{ωc1,ωc2,}] uses the frequency ωci for the ^(th) dimension.
  • LowpassFilter[data,ωc] uses a filter kernel length and smoothing window suitable for the cutoff frequency ωc and the input data.
  • Typical smoothing windows wfun include:
  • BlackmanWindowsmoothing with a Blackman window
    DirichletWindowno smoothing
    HammingWindowsmoothing with a Hamming window (default)
    {v1,v2,}use a window with values vi
    fcreate a window by sampling f between and
  • The following options can be given:
  • Padding"Fixed"the padding value to use
    SampleRateAutomaticsample rate assumed for the input
  • By default, SampleRate->1 is assumed for images as well as lists. For audio signals and time series, the sample rate is either extracted or computed from the input data.
  • With SampleRate->r, the cutoff frequency ωc should be between 0 and . »

Examples

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Basic Examples  (3)

Lowpass filtering of a noisy square wave:

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Lowpass filtering of audio:

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Lowpass filtering of an image:

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Scope (13)

Options (4)

Applications (3)

Properties & Relations (4)

Possible Issues (1)

Interactive Examples (1)

See Also

HighpassFilter  BandpassFilter  BandstopFilter  DifferentiatorFilter  HilbertFilter  LeastSquaresFilterKernel  ListConvolve  ImageConvolve  MeanFilter  GaussianFilter

Introduced in 2012
(9.0)
| Updated in 2016
(11.0)