nag_fft_init_trig (c06gzc) (PDF version)
c06 Chapter Contents
c06 Chapter Introduction
NAG Library Manual
NAG Library Function Document
nag_fft_init_trig (c06gzc)
+
−
Contents
1
Purpose
2
Specification
3
Description
4
References
5
Arguments
6
Error Indicators and Warnings
7
Accuracy
8
Parallelism and Performance
9
Further Comments
+
−
10
Example
10.1
Program Text
10.2
Program Data
10.3
Program Results
1 Purpose
nag_fft_init_trig (c06gzc) calculates the trigonometric coefficients required for the computation of discrete Fourier transforms.
2 Specification
#include <nag.h>
#include <nagc06.h>
void
nag_fft_init_trig (Integer
n
, double
trig
[], NagError *
fail
)
3 Description
This is a utility function for use in conjunction with one or more of
nag_fft_multiple_real (c06fpc)
,
nag_fft_multiple_hermitian (c06fqc)
,
nag_fft_multiple_complex (c06frc)
,
nag_fft_2d_complex (c06fuc)
,
nag_fft_multiple_sine (c06hac)
,
nag_fft_multiple_cosine (c06hbc)
,
nag_fft_multiple_qtr_sine (c06hcc)
and
nag_fft_multiple_qtr_cosine (c06hdc)
. nag_fft_init_trig (c06gzc) initializes the array
trig
with trigonometric coefficients according to the value of
n
and must be called prior to the first call of one of the above listed functions.
4 References
None.
5 Arguments
1:
n
–
Integer
Input
On entry
: the value of
n
in the Fourier transform function being called.
Constraint
:
n
≥
1
.
2:
trig
[
2
×
n
]
–
double
Output
On exit
: the trigonometric coefficients are stored in
trig
.
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
≥
1
.
7 Accuracy
Exact.
8 Parallelism and Performance
Not applicable.
9 Further Comments
None.
10 Example
The program reads in 3 real data sequences and prints their discrete Fourier transforms in Hermitian format as calculated by
nag_fft_multiple_real (c06fpc)
. A call is made to nag_fft_init_trig (c06gzc) to initialize the array
trig
prior to calling
nag_fft_multiple_real (c06fpc)
. The transforms are then printed out in full complex form after a call to
nag_multiple_hermitian_to_complex (c06gsc)
.
10.1 Program Text
Program Text (c06gzce.c)
10.2 Program Data
Program Data (c06gzce.d)
10.3 Program Results
Program Results (c06gzce.r)
nag_fft_init_trig (c06gzc) (PDF version)
c06 Chapter Contents
c06 Chapter Introduction
NAG Library Manual
© The Numerical Algorithms Group Ltd, Oxford, UK. 2014