NAG Library Function Document

nag_conjugate_hermitian (c06gbc)

This is a utility function for use in conjunction with nag_fft_real (c06eac) and nag_fft_hermitian (c06ebc), to calculate inverse discrete Fourier transforms.

4 References

None.

5 Arguments

1: n – IntegerInput: On entry: the number of data values, $n$ .
Constraint: $n \geq 1$ .
2: x[n] – doubleInput/Output: On entry: if the data values $z_{j}$ are written as $x_{j} + i y_{j}$ , then for $0 \leq j \leq n / 2$ , $x [j]$ must contain $x_{j} (= x_{n - j})$ , while for $n / 2 < j \leq n - 1$ , $x [j]$ must contain $- y_{j} (= y_{n - j})$ . In other words, x must contain the Hermitian sequence in Hermitian form.

On exit: the imaginary parts $y_{j}$ are negated. The real parts $x_{j}$ are not referenced.
3: fail – NagError *Input/Output: The NAG error argument (see Section 3.6 in the Essential Introduction).

6 Error Indicators and Warnings

NE_INT_ARG_LT: On entry, $n = ⟨value⟩$ .
Constraint: $n \geq 1$ .

7 Accuracy

Exact.

8 Parallelism and Performance

Not applicable.

9 Further Comments

The time taken is negligible.

10 Example

This program reads in a sequence of real data values, calls nag_fft_real (c06eac) followed by nag_conjugate_hermitian (c06gbc) to compute their inverse discrete Fourier transform, and prints this after expanding it from Hermitian form into a full complex sequence.

NAG Library Function Documentnag_conjugate_hermitian (c06gbc)

+− Contents

1 Purpose

2 Specification

3 Description