# poly2ccw

Convert polygon contour to counterclockwise vertex ordering

## Syntax

```[x2,y2] = poly2ccw(x1,y1) ```

## Description

`[x2,y2] = poly2ccw(x1,y1)` arranges the Cartesian vertices in the polygonal contour (`x1,y1`) in counterclockwise order, returning the result in `x2` and `y2`. If `x1` and `y1` can contain multiple contours, represented either as `NaN`-separated vectors or as cell arrays, then each contour is converted to clockwise ordering. `x2` and `y2` have the same format (`NaN`-separated vectors or cell arrays) as `x1` and `y1`.

## Examples

Convert a clockwise-ordered square to counterclockwise ordering.

```x1 = [0 0 1 1 0]; y1 = [0 1 1 0 0]; ispolycw(x1, y1) ans = 1 [x2, y2] = poly2ccw(x1, y1); ispolycw(x2, y2) ans = 0```

## Tips

You can use `poly2ccw` for geographic coordinates if the polygon does not cross the Antimeridian or contain a pole. A polygon contains a pole if the longitude data spans 360 degrees. To use `poly2ccw` with geographic coordinates, specify the longitude vector as `x1` and the latitude vector as `y1`. 