centroid

Centroid of polyshape

Syntax

[x,y] = centroid(polyin)

[x,y] = centroid(polyin,I)

Description

[x,y] = centroid(polyin) returns the x-coordinates and the y-coordinates of the centroid of a polyshape.

[x,y] = centroid(polyin,I) returns the coordinates of the centroid of the Ith boundary of polyin.

This syntax is only supported when polyin is a scalar polyshape object.

Examples

Centroid of Polygon

Compute the centroids associated with a multiregion polygon.

Create a polygon containing two solid regions, and then compute its centroid.

x1 = [0 1 2];
y1 = [0 1 0];
x2 = [2 3 4];
y2 = [1 2 1];
polyin = polyshape({x1,x2},{y1,y2});
[x,y] = centroid(polyin);
plot(polyin)
hold on
plot(x,y,'r*')
hold off

To compute the centroid of each region separately, specify the boundary indices of each region in the second argument.

[x,y] = centroid(polyin,[1 2]);
plot(polyin)
hold on
plot(x(1),y(1),'r*',x(2),y(2),'r*')
hold off

Alternatively, you can compute the centroid of each region by first separating the regions into separate polyshape objects. Use the regions function to create an array of polyshape objects, where each element of the array is a polyshape defining one of the triangular regions.

polyarray = regions(polyin)

polyarray = 
  2x1 polyshape array with properties:

    Vertices
    NumRegions
    NumHoles

[x,y] = centroid(polyarray)

x = 2×1

     1
     3

y = 2×1

    0.3333
    1.3333

Input Arguments

polyin — Input polyshape

scalar | vector | matrix | multidimensional array

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

Data Types: polyshape

I — Boundary index

scalar integer | vector of integers

Boundary index, specified as a scalar integer or vector of integers. Each element of I corresponds to a single boundary of the input polyshape.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Output Arguments

x — x-coordinate

scalar | vector | matrix | multidimensional array

x-coordinate of the centroid of a polyshape, returned as a scalar, vector, matrix, or multidimensional array. If the input is an array of polyshape objects, then x contains the x-coordinates of the centroid of each polyshape.

y — y-coordinate

scalar | vector | matrix | multidimensional array

y-coordinate of the centroid of a polyshape, returned as a scalar, vector, matrix, or multidimensional array. If the input is an array of polyshape objects, then y contains the y-coordinates of the centroid of each polyshape.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Dynamic memory allocation must be enabled for code generation.

• Name-value pair must be compile time constant.

Version History

Introduced in R2017b