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MinFilter[data,r]

filters data by replacing every value by the minimum value in its range-r neighborhood.

MinFilter[data,{r1,r2,…}]

uses ri for filtering the ^(th)dimension in data.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Data  
Parameters  
Applications  
Properties & Relations  
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MinFilter

MinFilter[data,r]

filters data by replacing every value by the minimum value in its range-r neighborhood.

MinFilter[data,{r1,r2,…}]

uses ri for filtering the ^(th)dimension in data.

Details

  • MinFilter is a nonlinear filter commonly used to locally smooth data and diminish salt-like noise, where the amount of smoothing is dependent on the value of r.
  • The function applied to each range-r neighborhood is Min.
  • The data can be any of the following:
  • listarbitrary-rank numerical array
    tseriestemporal data such as TimeSeries, TemporalData, …
    imagearbitrary Image or Image3D object
    audioan Audio object
    videoa Video object
  • For multichannel images, MinFilter replaces each pixel by a pixel in its neighborhood that has the minimum total intensity, averaged over all channels.
  • MinFilter[data,{r1,r2,…}] computes the minimum value in blocks centered on each sample.
  • MinFilter assumes the index coordinate system for lists and images.
  • At the data boundaries, MinFilter uses smaller neighborhoods.

Examples

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Basic Examples  (3)

Minimum filter of a list:

Wolfram Language code: MinFilter[ {1, 2, 3, 2, 1}, 1]

Filter a TimeSeries:

Wolfram Language code: ts = TemporalData[TimeSeries, {{{0., -0.054108337548928784, 0.1280211704499059, 0.28162021808461324, -0.2057320325139802, -0.4871901025739722, -0.7154387408784426, -0.7399660905024047, -0.6981022018441507, -0.7178077145466483, -0.8034462541874 ... 7894984276149, 1.8851123992920942, 1.8341759268762767, 2.0335844117979263}}, {{0., 10., 0.1}}, 1, {"Continuous", 1}, {"Continuous", 1}, 1, {ValueDimensions -> 1, ResamplingMethod -> {"Interpolation", InterpolationOrder -> 1}}}, False, 10.];
Wolfram Language code: filtered = MinFilter[ts, 0.5]
Wolfram Language code: ListLinePlot[{ts, filtered}, PlotLegends -> {"original data", "filtered"}]

Minimum filtering of a color image:

Wolfram Language code: MinFilter[[image], 6]

Scope  (13)

Data  (8)

Minimum filtering of a numeric vector:

Wolfram Language code: MinFilter[{0, 3, 8, 2}, 1]

Filtering a symbolic array:

Wolfram Language code: MinFilter[ {a, b, c}, 1]

Minimum filtering of a 2D array:

Wolfram Language code: MinFilter[(⁠| | | | | | - | - | - | - | | 0 | 3 | 8 | 2 | | 7 | 6 | 9 | 6 | | 5 | 8 | 4 | 0 | | 3 | 5 | 1 | 6 |⁠), 1]//MatrixForm

Minimum filtering of a list of Quantity objects:

Wolfram Language code: data = {Quantity[9, "Feet"], Quantity[86, "Inches"], Quantity[27.1, "Meters"], Quantity[79, "Feet"], Quantity[90, "Feet"], Quantity[41, "Inches"], Quantity[99, "Inches"], Quantity[6, "Feet"], Quantity[38, "Feet"], Quantity[89, "Feet"], Quantity[53, "Feet"], Quantity[85, "Meters"], Quantity[92, "Meters"], Quantity[95, "Meters"], Quantity[49, "Feet"]};
Wolfram Language code: ListLinePlot[{data, MinFilter[data, 2]}, PlotRange -> All]

Filter an Audio signal:

Wolfram Language code: a = Import["ExampleData/rule30.wav"];
Wolfram Language code: b = MinFilter[a, 35]
Wolfram Language code: AudioPlot[{a, b}]

Filtering a 2D grayscale image:

Wolfram Language code: MinFilter[[image], 3]

Filter video frames:

Wolfram Language code: MinFilter[Video["ExampleData/fish.mp4"], 2]

Minimum filter of a 3D image:

Wolfram Language code: MinFilter[[image], 2]

Parameters  (5)

Specify one radius to be used in all directions:

Wolfram Language code: MinFilter[[image], 1]

Increasing the radius will result in darker images:

Wolfram Language code: Table[Labeled[MinFilter[[image], r], Text["*r* = " <> ToString@r]], {r, {1, 2, 4}}]

Minimum filtering just in the first direction:

Wolfram Language code: MinFilter[[image], {5, 0}]

Filtering just in the second direction:

Wolfram Language code: MinFilter[[image], {0, 5}]

Minimum filtering of a 3D image in the vertical direction only:

Wolfram Language code: MinFilter[[image], {4, 0, 0}]

Filtering of a 3D image in the horizontal planes only:

Wolfram Language code: MinFilter[[image], {0, 4, 4}]

Applications  (3)

Use minimum filtering to remove thin, bright objects:

Wolfram Language code: MinFilter[[image], 1]

Remove salt noise from an image:

Wolfram Language code: MinFilter[[image], 1]

Use minimum filtering to locate borders in an image:

Wolfram Language code: i = [image]; ImageSubtract[i, MinFilter[i, 1]]

Properties & Relations  (2)

For single-channel images, MinFilter is the same as ImageFilter with function Min:

Wolfram Language code: MinFilter[[image], 1] == ImageFilter[Min, [image], 1]

For single-channel images, MinFilter is the same as Erosion with a box structuring element:

Wolfram Language code: MinFilter[[image], 1] == Erosion[[image], 1]
Wolfram Research (2008), MinFilter, Wolfram Language function, https://reference.wolfram.com/language/ref/MinFilter.html (updated 2025).

Text

Wolfram Research (2008), MinFilter, Wolfram Language function, https://reference.wolfram.com/language/ref/MinFilter.html (updated 2025).

CMS

Wolfram Language. 2008. "MinFilter." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2025. https://reference.wolfram.com/language/ref/MinFilter.html.

APA

Wolfram Language. (2008). MinFilter. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MinFilter.html

BibTeX

@misc{reference.wolfram_2026_minfilter, author="Wolfram Research", title="{MinFilter}", year="2025", howpublished="\url{https://reference.wolfram.com/language/ref/MinFilter.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_minfilter, organization={Wolfram Research}, title={MinFilter}, year={2025}, url={https://reference.wolfram.com/language/ref/MinFilter.html}, note=[Accessed: 12-June-2026]}