MatchRate is an After Effects script for extending a layer property’s animation at the same rate.

Instructions

1. Select two keyframes and click ‘Get Rate.’ The rate of the animation will load.
2. Select the layer whose animation you want to change (it can be the same layer)
3. Select the keyframe you want as the start of your new animation.
4. Move the playhead to where you want the animation extended.
5. Click ‘Apply Rate’ and the script write a new keyframe to the layer at the matched rate.*

* You can also choose which property dimension you’d like to target and at what percentage of the rate you’d like to apply the new keyframe.