---
title: "CGAffineTransformRotate(_:_:)"
framework: coregraphics
role: symbol
role_heading: Function
path: "coregraphics/cgaffinetransformrotate(_:_:)"
---

# CGAffineTransformRotate(_:_:)

Returns an affine transformation matrix constructed by rotating an existing affine transform.

## Declaration

```swift
func CGAffineTransformRotate(_ t: CGAffineTransform, _ angle: CGFloat) -> CGAffineTransform
```

## Parameters

- `t`: An existing affine transform.
- `angle`: The angle, in radians, by which to rotate the affine transform. In iOS, a positive value specifies counterclockwise rotation and a negative value specifies clockwise rotation. In macOS, a positive value specifies clockwise rotation and a negative value specifies counterclockwise rotation.

## Return Value

Return Value A new affine transformation matrix.

## Discussion

Discussion You use this function to create a new affine transformation matrix by adding a rotation value to an existing affine transform. The resulting structure represents a new affine transform, which you can use (and reuse, if you want) to rotate a coordinate system. The actual direction of rotation is dependent on the coordinate system orientation of the target platform, which is different in iOS and macOS.

## See Also

### Modifying Affine Transformations

- [CGAffineTransformTranslate(_:_:_:)](coregraphics/cgaffinetransformtranslate(_:_:_:).md)
- [CGAffineTransformScale(_:_:_:)](coregraphics/cgaffinetransformscale(_:_:_:).md)
- [CGAffineTransformInvert(_:)](coregraphics/cgaffinetransforminvert(_:).md)
- [CGAffineTransformConcat(_:_:)](coregraphics/cgaffinetransformconcat(_:_:).md)