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Wolfram Language & System Documentation Center
RegionMember
  • See Also
    • Element
    • RegionMemberFunction
    • RegionDistance
    • SignedRegionDistance
    • RegionEqual
    • RegionWithin
    • MemberQ
    • Between
    • GeometricScene
  • Related Guides
    • Region Properties and Measures
    • Polygons
    • Solid Geometry
    • Plane Geometry
    • Polyhedra
    • Synthetic Geometry
    • Interval Arithmetic
    • See Also
      • Element
      • RegionMemberFunction
      • RegionDistance
      • SignedRegionDistance
      • RegionEqual
      • RegionWithin
      • MemberQ
      • Between
      • GeometricScene
    • Related Guides
      • Region Properties and Measures
      • Polygons
      • Solid Geometry
      • Plane Geometry
      • Polyhedra
      • Synthetic Geometry
      • Interval Arithmetic

RegionMember[reg,{x,y,…}]

gives True if the numeric point {x,y,…} is a member of the constant region reg and False otherwise.

RegionMember[reg,{x,y,…}]

gives conditions for the point {x,y,…} to be a member of reg.

RegionMember[reg]

returns a RegionMemberFunction[…] that can be applied repeatedly to different points.

Details
Details and Options Details and Options
Examples  
Basic Examples  
Scope  
Basic Uses  
Special Regions  
Formula Regions  
Mesh Regions  
Derived Regions  
Applications  
Basic  
Random Points in a Region  
Monte Carlo Integration  
Properties & Relations  
See Also
Related Guides
History
Cite this Page
BUILT-IN SYMBOL
  • See Also
    • Element
    • RegionMemberFunction
    • RegionDistance
    • SignedRegionDistance
    • RegionEqual
    • RegionWithin
    • MemberQ
    • Between
    • GeometricScene
  • Related Guides
    • Region Properties and Measures
    • Polygons
    • Solid Geometry
    • Plane Geometry
    • Polyhedra
    • Synthetic Geometry
    • Interval Arithmetic
    • See Also
      • Element
      • RegionMemberFunction
      • RegionDistance
      • SignedRegionDistance
      • RegionEqual
      • RegionWithin
      • MemberQ
      • Between
      • GeometricScene
    • Related Guides
      • Region Properties and Measures
      • Polygons
      • Solid Geometry
      • Plane Geometry
      • Polyhedra
      • Synthetic Geometry
      • Interval Arithmetic

RegionMember

RegionMember[reg,{x,y,…}]

gives True if the numeric point {x,y,…} is a member of the constant region reg and False otherwise.

RegionMember[reg,{x,y,…}]

gives conditions for the point {x,y,…} to be a member of reg.

RegionMember[reg]

returns a RegionMemberFunction[…] that can be applied repeatedly to different points.

Details

  • RegionMember is also known as point in region test, membership test, and membership conditions.
  • A constant region is a region where ConstantRegionQ[reg] gives True.

Examples

open all close all

Basic Examples  (3)

Test whether a particular point is in a region:

Get conditions for point membership:

Create RegionMemberFunction to apply to different points:

Scope  (21)

Basic Uses  (4)

Directly test whether a point is in a region:

Directly test whether a list of points is in a region:

Get conditions for point membership by using variables {x,y}:

Create RegionMemberFunction to apply to different points:

Special Regions  (6)

Regions in :

Regions in :

Visualize region membership in :

Get the region bounds:

Uniformly sample over the bounding box for the region:

Regions in :

Visualize region membership in :

Regions in :

Formula Regions  (3)

Implicit regions:

Visualize region membership in :

Get the region bounds:

Uniformly sample over the bounding box for the region:

Parametric regions:

Mesh Regions  (4)

MeshRegion in 2D:

In 3D:

BoundaryMeshRegion in 2D:

BoundaryMeshRegion in 3D:

Derived Regions  (4)

RegionIntersection of two regions:

Get the region bounds:

Uniformly sample over the bounding box for the region:

RegionUnion of mixed-dimensional regions:

TransformedRegion:

RegionBoundary:

Applications  (6)

Basic  (2)

Convert polygon data for the given country to a MeshRegion:

Determine membership of a city:

For a parameterized region, RegionMember can give conditions on the parameters to determine when a given point is a member:

Find an instance where the region includes the point:

Visualize it:

Random Points in a Region  (2)

Generate points on a region by filtering a uniform set of points:

Get the region bounds:

Uniformly sample over the bounding box of the region:

Select member points:

Visualize member points:

Convert polygon data for the given country to a MeshRegion:

Get the region bounds:

Uniformly sample over the bounding box of the region:

Monte Carlo Integration  (2)

Perform Monte Carlo integration to estimate the area of a unit disk:

Get the region bounds:

Uniformly sample over the bounding box of the region:

Count the number of samples inside the region:

Get the ratio of samples inside the region to the total number of sample points:

Get the bounding area:

Get the approximate area of the region:

Use random points in a region to perform Monte Carlo integration:

Evaluate a function at each sample point and take their average:

Compare with the exact value:

Properties & Relations  (5)

Element can be used to test region membership for constant regions:

RegionDistance is 0 for a member:

SignedRegionDistance is non-positive for a member:

SignedRegionDistance is positive for a non-member:

Use RegionNearest to find the nearest member:

Visualize it:

Use FindInstance to find multiple instances for special and formula regions:

Find points that are in both regions:

See Also

Element  RegionMemberFunction  RegionDistance  SignedRegionDistance  RegionEqual  RegionWithin  MemberQ  Between  GeometricScene

Related Guides

    ▪
  • Region Properties and Measures
  • ▪
  • Polygons
  • ▪
  • Solid Geometry
  • ▪
  • Plane Geometry
  • ▪
  • Polyhedra
  • ▪
  • Synthetic Geometry
  • ▪
  • Interval Arithmetic

History

Introduced in 2014 (10.0)

Wolfram Research (2014), RegionMember, Wolfram Language function, https://reference.wolfram.com/language/ref/RegionMember.html.

Text

Wolfram Research (2014), RegionMember, Wolfram Language function, https://reference.wolfram.com/language/ref/RegionMember.html.

CMS

Wolfram Language. 2014. "RegionMember." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/RegionMember.html.

APA

Wolfram Language. (2014). RegionMember. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/RegionMember.html

BibTeX

@misc{reference.wolfram_2025_regionmember, author="Wolfram Research", title="{RegionMember}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/RegionMember.html}", note=[Accessed: 01-March-2026]}

BibLaTeX

@online{reference.wolfram_2025_regionmember, organization={Wolfram Research}, title={RegionMember}, year={2014}, url={https://reference.wolfram.com/language/ref/RegionMember.html}, note=[Accessed: 01-March-2026]}

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