---
title: "velocity(at:)"
framework: swiftui
role: symbol
role_heading: Instance Method
path: "swiftui/unitcurve/velocity(at:)"
---

# velocity(at:)

Returns the rate of change (first derivative) of the output value of the curve at the given time.

## Declaration

```swift
func velocity(at progress: Double) -> Double
```

## Parameters

- `progress`: The input progress (x component). The provided value is clamped to the range [0,1].

## Return Value

Return Value The velocity of the output value (y component) of the curve at the given time.

## See Also

### Getting curve characteristics

- [value(at:)](swiftui/unitcurve/value(at:).md)