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xor

Exclusive OR of two polyshape objects

Description

example

polyout = xor(poly1,poly2) returns a polyshape object whose regions are the geometric exclusive OR of two polyshape objects. The geometric exclusive OR contains the regions of poly1 and poly2 that do not overlap. poly1 and poly2 must have compatible array sizes.

example

[polyout,shapeID,vertexID] = xor(poly1,poly2) also returns vertex mapping information from the vertices in polyout to the vertices in poly1 and poly2. The xor function only supports this syntax when poly1 and poly2 are scalar polyshape objects.

The shapeID elements identify whether the corresponding vertex in polyout originated in poly1, poly2, or was created from the exclusive OR. vertexID maps the vertices of polyout to the vertices of poly1, poly2, or the exclusive OR.

___ = xor(poly1,poly2,'KeepCollinearPoints',TF) specifies whether to keep or remove collinear points in polyout for any of the previous syntaxes.

Examples

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Create and plot two polygons.

poly1 = polyshape([0 0 1 1],[1 0 0 1]);
poly2 = polyshape([0.75 1.25 1.25 0.75],[0.25 0.25 0.75 0.75]);
plot(poly1)
hold on
plot(poly2)

Figure contains an axes object. The axes object contains 2 objects of type polygon.

figure

Compute and plot the exclusive OR of poly1 and poly2.

polyout = xor(poly1,poly2)
polyout = 
  polyshape with properties:

      Vertices: [13x2 double]
    NumRegions: 2
      NumHoles: 0

plot(polyout)

Figure contains an axes object. The axes object contains an object of type polygon.

Create two polygons, and compute and plot their exclusive OR. Display the vertex coordinates of the exclusive OR and the corresponding vertex mapping information.

poly1 = polyshape([0 0 1 1],[1 0 0 1]);
poly2 = translate(poly1,[0.5 0]);
[polyout,shapeID,vertexID] = xor(poly1,poly2);
plot(polyout)

Figure contains an axes object. The axes object contains an object of type polygon.

[polyout.Vertices shapeID vertexID]
ans = 9×4

         0    1.0000    1.0000    1.0000
    0.5000    1.0000    2.0000    1.0000
    0.5000         0    2.0000    4.0000
         0         0    1.0000    4.0000
       NaN       NaN       NaN       NaN
    1.0000    1.0000    1.0000    2.0000
    1.5000    1.0000    2.0000    2.0000
    1.5000         0    2.0000    3.0000
    1.0000         0    1.0000    3.0000

There are two boundaries in the exclusive OR, separated by a row of NaN values in the Vertices property. For example, consider the first boundary in the array. The first and last vertices of the exclusive OR originated in poly1, since the corresponding values in shapeID are 1. These vertices are the first and fourth vertices in the property poly1.Vertices, respectively, since the corresponding values in vertexID are 1 and 4. Similarly, the second and third vertices of the exclusive OR originated in poly2, and they are also the first and fourth vertices in the property poly2.Vertices, respectively.

Input Arguments

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First input polyshape, specified as a scalar, vector, matrix, or multidimensional array.

Second input polyshape, specified as a scalar, vector, matrix, or multidimensional array.

Collinear vertices indicator, specified as false or true:

  • false — Remove collinear points so that the output polyshape contains the fewest vertices necessary to define the boundaries.

  • true — Keep all collinear points as vertices.

When the 'KeepCollinearPoints' parameter is not specified, its value is assigned according to the values used when creating the input polyshape objects:

  • If the value was true for each input polyshape when they were created, then the value for the output polyshape is set to true.

  • If the value was false for each input polyshape when they were created, then the value for the output polyshape is set to false.

  • If the values for the input polyshape objects do not match, then the value for the output polyshape is set to false.

Data Types: logical

Output Arguments

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Output polyshape, returned as a scalar, vector, matrix, or multidimensional array.

The two input polyshape arguments must have compatible sizes. For example, if two input polyshape vectors have different lengths M and N, then they must have different orientations (one must be a row vector and one must be a column vector). polyout is then M-by-N or N-by-M depending on the orientation of each input vector. For more information on compatible array sizes, see Compatible Array Sizes for Basic Operations.

Shape ID, returned as a column vector whose elements each represent the origin of the vertex in the exclusive OR. The value of an element in shapeID is 0 when the corresponding vertex of the output polyshape was created by the exclusive OR. An element is 1 when the corresponding vertex originated from poly1, and 2 when it originated from poly2.

The length of shapeID is equal to the number of rows in the Vertices property of the output polyshape. The xor function only supports this output argument if the input polyshape objects are scalar.

Data Types: double

Vertex ID, returned as a column vector whose elements map the vertices in the output polyshape to the vertices in the polyshape of origin. The elements of vertexID contain the row numbers of the corresponding vertices in the Vertices property of the input polyshape. An element is 0 when the corresponding vertex of the output polyshape was created by the exclusive OR.

The length of vertexID is equal to the number of rows in the Vertices property of the output polyshape. The xor function only supports this output argument when the input polyshape objects are scalar.

Data Types: double

Introduced in R2017b