# NAG CL Interfacec06gzc (init_​trig)

Note: this function is deprecated and will be withdrawn at Mark 30.2. There is no replacement for this function.

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## 1Purpose

c06gzc calculates the trigonometric coefficients required for the computation of discrete Fourier transforms.

## 2Specification

 #include
 void c06gzc (Integer n, double trig[], NagError *fail)
The function may be called by the names: c06gzc, nag_sum_init_trig or nag_fft_init_trig.

## 3Description

This is a utility function for use in conjunction with c06fpc and c06fqc. 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.

None.

## 5Arguments

1: $\mathbf{n}$Integer Input
On entry: the value of $n$ in the Fourier transform function being called.
Constraint: ${\mathbf{n}}\ge 1$.
2: $\mathbf{trig}\left[2×{\mathbf{n}}\right]$double Output
On exit: the trigonometric coefficients are stored in trig.
3: $\mathbf{fail}$NagError * Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

## 6Error Indicators and Warnings

NE_INT_ARG_LT
On entry, ${\mathbf{n}}=⟨\mathit{\text{value}}⟩$.
Constraint: ${\mathbf{n}}\ge 1$.

Exact.

## 8Parallelism and Performance

c06gzc is not threaded in any implementation.

None.

## 10Example

The program reads in 3 real data sequences and prints their discrete Fourier transforms in Hermitian format as calculated by c06fpc. A call is made to c06gzc to initialize the array trig prior to calling c06fpc. The transforms are then printed out in full complex form after a call to c06gsc.

### 10.1Program Text

Program Text (c06gzce.c)

### 10.2Program Data

Program Data (c06gzce.d)

### 10.3Program Results

Program Results (c06gzce.r)