vDSP_vlintD
Calculates the interpolation between the neighboring elements of a double-precision vector using the specified stride.
Declaration
extern void vDSP_vlintD(const double *__A, const double *__B, vDSP_Stride __IB, double *__C, vDSP_Stride __IC, vDSP_Length __N, vDSP_Length __M);Parameters
- __A:
The double-precision input vector.
- __B:
The vector that controls the interpolation. The integer part of each element in the control vector is the zero-based index of the first element of a pair of adjacent values in the source array. The fractional part defines the linear interpolation between the values at those indices.
- __IB:
The stride between elements in the vector
__B. - __C:
The double-precision output vector.
- __IC:
The stride between elements in the vector
__C. - __N:
The number of elements in the output vector.
- __M:
The number of elements in the input vector.
Mentioned in
Discussion
Performs the following operation:
for (int n = 0; n < N; ++n){
double b = B[n*IB];
double index = trunc(b); // The integer part of B.
double alpha = b - index; // The fractional part of B.
double a0 = A[(int)index]; // The indexed A value.
double a1 = A[(int)index + 1]; // The next indexed A value.
C[n*IC] = a0 + (alpha * (a1 -a0)); // The interpolated value.
}The function generates vector C by interpolating between neighboring values of vector A as controlled by vector B. The operation treats the integer portion of each element in B as the zero-based index of the first element of a pair of adjacent values in vector A.
The function uses the fractional part of the value in B to calculate the corresponding element of C from the two adjacent values.
The calculation doesn’t use the argument M. However, the integer parts of the values in B must be greater than or equal to zero and less than or equal to M - 2.