# vDSP_vrampmul2D Generates a double-precision, stereo ramped vector and multiplies that vector by an input vector. ``` void vDSP_vrampmul2D(const double *__I0, const double *__I1, vDSP_Stride __IS, double *__Start, const double *__Step, double *__O0, double *__O1, vDSP_Stride __OS, vDSP_Length __N); ``` ## Parameters `__I0` The first double-precision input vector. `__I1` The second double-precision input vector. `__IS` The stride for both input vectors. `__Start` On input, the initial value of the ramp. On output, the next value in the ramp. `__Step` The increment, or decrement if negative, between each generated element. `__O0` The first double-precision output vector. `__O1` The second double-precision output vector. `__OS` The stride for both output vectors. `__N` The number of elements that the function processes. ## Discussion The functions in this group function populate a vector, by multiplying the values in an input vector with the corresponding values of a ramp generated by the `Start` and `Step` parameters. The following code describes the calculation: ```c for (i = 0; i < N; ++i) { O[i*OS] = *Start * I[i*IS]; *Start += *Step; } ``` For example, the following code fills the array `i` with sine values: ```swift let n = vDSP_Length(1024) let i: [Float] = (0 ..< n).map { return sin(Float($0) / 20) } ``` The following illustrates the values of `i`:  Use `i` as the input vector to [`vDSP_vrampmul`](/documentation/Accelerate/vDSP_vrampmul): ```swift let stride = vDSP_Stride(1) var start: Float = 0 var step: Float = 0.1 var o = [Float](repeating: 0, count: Int(n)) vDSP_vrampmul(i, stride, &start, &step, &o, stride, n) ``` On return, the output vector, `o`, is filled with a ramped-sine wave:  --- 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)