sortboundaries

Sort polyshape boundaries

Syntax

polyout = sortboundaries(polyin,criterion,direction)

polyout = sortboundaries(polyin,'centroid',direction,'ReferencePoint',point)

Description

polyout = sortboundaries(polyin,criterion,direction) returns a polyshape object whose boundaries are sorted according to the specified criterion and direction. For example, polyout = sortboundaries(polyin,'area','ascend') returns a polyshape whose boundaries are the same as polyin. polyout lists the boundaries in ascending order by their area.

polyout = sortboundaries(polyin,'centroid',direction,'ReferencePoint',point) returns a polyshape whose boundaries are sorted based on the distance of the centroid of each boundary to a reference point.

Examples

Sort by Number of Sides

Sort the boundaries of a polygon according to their number of sides in order to access a single boundary at a time.

Create a polygon containing two boundaries, one with three sides and one with four sides.

x1 = [0 1 1 0];
y1 = [0 0 1 1];
x2 = [2 3 2.5];
y2 = [2 2 3];
polyin = polyshape({x1,x2},{y1,y2});
plot(polyin)

Sort the boundaries in descending order according to their number of sides, so that the four-sided boundary is indexed first in the output polyshape object.

polyout = sortboundaries(polyin,'numsides','descend');

You now can reference the four-sided boundary based on its index, for example when you want to access the boundary's vertices or compute its area.

[x,y] = boundary(polyout,1)

x = 5×1

     0
     0
     1
     1
     0

y = 5×1

     0
     1
     1
     0
     0

area(polyout,1)

ans = 
1

Input Arguments

polyin — Input polyshape

scalar | vector | matrix | multidimensional array

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

Data Types: polyshape

criterion — Sort criterion

'area' | 'perimeter' | 'numsides' | 'centroid'

Sort criterion, specified as one of these values:

• 'area' — Sort by boundary area.

• 'perimeter' — Sort by boundary perimeter.

• 'numsides' — Sort by the number of sides of each boundary.

• 'centroid' — Sort by the distance from the centroid of each boundary to the reference point (0,0).

direction — Sort direction

'ascend' | 'descend'

Sort direction, specified as 'ascend' or 'descend'.

point — Reference point

[0 0] | two-element row vector

Reference point, specified as a two-element row vector. The first element is the x-coordinate of the reference point, and the second element is the y-coordinate.

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 arguments must be compile time constant.

• The order of boundaries in the output polyshape object might differ from that in MATLAB. However, the boundaries will be sorted based on the specified input criterion.

Version History

Introduced in R2017b