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# init(from:by:timing:isAdditive:)

Creates a new action that interpolates towards a specified value, which
is relative to the starting value.

```
init(from: Value? = nil, by: Value, timing: AnimationTimingFunction = .linear, isAdditive: Bool = false)
```

## Parameters

`from`

Value set at the start of the animation, or `nil` to use the default source.

`by`

Value relative to the initial value to determine the final value.

`timing`

Controls the progress of the animation.

`isAdditive`

Specifies whether you can additively blend the output from the action’s animation.

## Discussion

`from` → `from + by` or `defaultSource` → `defaultSource + by`

---

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