# formStereoRamp(withInitialValue:multiplyingBy:_:increment:results:_:) Populates two single-precision vectors that contain stereo monotonically incrementing or decrementing values multiplied by two source vectors. ``` static func formStereoRamp(withInitialValue initialValue: inout Float, multiplyingBy multiplierOne: U, _ multiplierTwo: U, increment: Float, results resultOne: inout V, _ resultTwo: inout V) where U : AccelerateBuffer, V : AccelerateMutableBuffer, U.Element == Float, V.Element == Float ``` ## Parameters `initialValue` The initial value of the ramp. `multiplierOne` The first input vector that’s multiplied by the ramp function. `multiplierTwo` The second input vector that’s multiplied by the ramp function. `increment` The increment, or decrement if negative, between each generated element. `resultOne` The increment, or decrement if negative, between each generated element. `resultTwo` The array to overwrite with the first generated ramp. ## Discussion Use this function to populate two vectors by multiplying the values in two input vectors with the corresponding values of a ramp. For example, the following code fills the arrays `multiplierOne` and `multiplierTwo` with sine values: ```swift let n = vDSP_Length(1024) let multiplierOne: [Float] = (0 ..< n).map { return sin(Float($0) / 20) * 2 } let multiplierTwo: [Float] = (0 ..< n).map { return sin(Float($0) / 40) } ``` The following figure illustrates the values of `multiplierOne`, as a solid line, and `multiplierTwo`, as a dashed line:  Pass `multiplierOne` and `multiplierTwo` as the `multiplyingBy` parameter of [`formStereoRamp(withInitialValue:multiplyingBy:_:increment:results:_:)`](/documentation/Accelerate/vDSP/formStereoRamp(withInitialValue:multiplyingBy:_:increment:results:_:)-9be28): ```swift var start: Float = 0 let step: Float = 0.1 var resultOne = [Float](repeating: 0, count: Int(n)) var resultTwo = [Float](repeating: 0, count: Int(n)) vDSP.formStereoRamp(withInitialValue: &start, multiplyingBy: multiplierOne, multiplierTwo, increment: step, results: &resultOne, &resultTwo) ``` On return, the output vectors, `results.firstOutput` and `results.secondOutput`, contain ramped-sine waves. The figure below shows the first output as a solid line and the second output as a dashed line:  --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)