vDSP_vgenpD

Declaration

extern void vDSP_vgenpD(const double *__A, vDSP_Stride __IA, const double *__B, vDSP_Stride __IB, double *__C, vDSP_Stride __IC, vDSP_Length __N, vDSP_Length __M);

Parameters

• __A:

  The input vector that defines the values that the function interpolates.

• __IA:

  The distance between the elements in the values vector.

• __B:

  The input vector that defines the indices at which the function interpolates.

• __IB:

  The distance between the elements in the indices vector.

• __C:

  The output vector.

• __IC:

  The distance between the elements in the output vector.

• __N:

  The number of elements that the function processes.

• __M:

  The number of elements in the values and indices input vectors.

Mentioned in

• Using linear interpolation to construct new data points

Discussion

The following code creates a five-element vector from two values using linear interpolation. The last index in indices determines the length of the operation result.

    let values: [Double] = [0, 100]
    let indices: [Double] = [0, 4]
    
    let n = Int(indices.last! + 1)
    let m = values.count
    
    let stride = 1
    
    let interpolatedValues = [Double](unsafeUninitializedCapacity: n) {
        buffer, initializedCount in
        
        vDSP_vgenpD(values, stride,
                    indices, stride,
                    buffer.baseAddress!, stride,
                    vDSP_Length(n),
                    vDSP_Length(m))
        
        initializedCount = n
    }
    
    // Prints "[0.0, 25.0, 50.0, 75.0, 100.0]".
    print(interpolatedValues)

See Also

Vector generation by extrapolation and interpolation

• vDSP_vgenp