poly2cw

Convert polygon vertices to clockwise order

Syntax

[x2,y2] = poly2cw(x1,y1)

Description

[x2,y2] = poly2cw(x1,y1) arranges the Cartesian vertices of the polygon defined by x1 and y1 so the vertices are in clockwise order.

Examples

Convert Vertices to Clockwise Order

Specify a polygon using vertices in counterclockwise order. Close the polygon by repeating the first vertex at the end of the list.

x1 = [0 3 4 1 0];
y1 = [0 2 3 1 0];
ispolycw(x1,y1)

ans = logical
   0

Arrange the vertices so they are in clockwise order.

[x2,y2] = poly2cw(x1,y1);
ispolycw(x2,y2)

ans = logical
   1

Input Arguments

x1 — x-coordinates of polygon

numeric vector | cell array of numeric vectors

x-coordinates of the polygon, specified as a numeric vector or a cell array of numeric vectors.

• Define one polygon by specifying a vector, such as [39 45 19 39].

• Define multiple polygons by using one of these options:

  • Specify a vector and separate the polygons using NaN values, such as [37 46 31 20 37 NaN 45 49 35 32 45 NaN 35 40 42 35]. The NaN values in x1 must correspond to the NaN values in y1.

  • Specify a cell array of vectors, such as {[37 46 31 20 37],[45 49 35 32 45],[35 40 42 35]}. The size of the vector in each cell of x1 must match the size of the vector in the corresponding cell of y1.

The size and type of x1 must match the size and type of y1.

y1 — y-coordinates of polygon

numeric vector | cell array of numeric vectors

y-coordinates of the polygon, specified as a numeric vector or a cell array of numeric vectors.

• Define one polygon by specifying a vector, such as [-113 -49 -100 -113].

• Define multiple polygons by using one of these options:

  • Specify a vector and separate the polygons using NaN values, such as [69 90 105 79 69 NaN 6 52 43 14 6 NaN 18 32 22 18]. The NaN values in y1 must correspond to the NaN values in x1.

  • Specify a cell array of vectors, such as {[69 90 105 79 69],[6 52 43 14 6],[18 32 22 18]}. The size of the vector in each cell of y1 must match the size of the vector in the corresponding cell of x1.

The size and type of y1 must match the size and type of x1.

Output Arguments

x2 — x-coordinates in clockwise order

numeric vector | cell array of numeric vectors

x-coordinates in clockwise order, returned as a numeric vector or a cell array of numeric vectors.

When x1 and y1 define multiple polygons, the poly2cw function converts the coordinates of each individual polygon to clockwise order.

The size and type of x2 matches the size and type of x1.

Data Types: double

y2 — y-coordinates in clockwise order

numeric vector | cell array of numeric vectors

y-coordinates in clockwise order, returned as a numeric vector or a cell array of numeric vectors.

When x1 and y1 define multiple polygons, the poly2cw function converts the coordinates of each individual polygon to clockwise order.

The size and type of y2 matches the size and type of y1.

Data Types: double

Tips

You can specify geographic coordinates as input to the poly2cw function when the polygon does not cross the Antimeridian or contain a pole. A polygon contains a pole when the longitude data spans 360 degrees. To use geographic coordinates as input, specify x1 using the longitude vector and y1 using the latitude vector.

Version History

Introduced before R2006a