NAG Library Function Document

nag_dwt (c09cac)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:    $\mathbf{n}$ – IntegerInput

On entry: the number of elements, $n$, in the data array $x$.

Constraint: this must be the same as the value n passed to the initialization function nag_wfilt (c09aac).

2:    $\mathbf{x}\left[\mathbf{n}\right]$ – const doubleInput

On entry: x contains the input dataset $x_{\mathit{i}}$, for $\mathit{i}=1,2,\dots ,n$.

3:    $\mathbf{lenc}$ – IntegerInput

On entry: the dimension of the arrays ca and cd. This must be at least the number, $n_c$, of approximation coefficients, $C_a$, and detail coefficients, $C_d$, of the discrete wavelet transform as returned in nwc by the call to the initialization function nag_wfilt (c09aac).

Constraint: $\mathbf{lenc}\ge n_c$, where $n_c$ is the value returned in nwc by the call to the initialization function nag_wfilt (c09aac).

4:    $\mathbf{ca}\left[\mathbf{lenc}\right]$ – doubleOutput

On exit: $\mathbf{ca}\left[i-1\right]$ contains the $i$th approximation coefficient, $C_a\left(\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,n_c$.

5:    $\mathbf{cd}\left[\mathbf{lenc}\right]$ – doubleOutput

On exit: $\mathbf{cd}\left[\mathit{i}-1\right]$ contains the $\mathit{i}$th detail coefficient, $C_d\left(\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,n_c$.

6:    $\mathbf{icomm}\left[100\right]$ – IntegerCommunication Array

On entry: contains details of the discrete wavelet transform and the problem dimension as setup in the call to the initialization function nag_wfilt (c09aac).

On exit: contains additional information on the computed transform.

7:    $\mathbf{fail}$ – NagError *Input/Output

The NAG error argument (see Section 3.7 in How to Use the NAG Library and its Documentation).

6

Error Indicators and Warnings

NE_ALLOC_FAIL

Dynamic memory allocation failed.
See Section 2.3.1.2 in How to Use the NAG Library and its Documentation for further information.

NE_ARRAY_DIM_LEN

On entry, array dimension lenc not large enough: $\mathbf{lenc}=〈\mathit{\text{value}}〉$ but must be at least $〈\mathit{\text{value}}〉$.

NE_BAD_PARAM

On entry, argument $〈\mathit{\text{value}}〉$ had an illegal value.

NE_INITIALIZATION

Either the initialization function has not been called first or array icomm has been corrupted.

Either the initialization function was called with $\mathbf{wtrans}=\mathrm{Nag\_MultiLevel}$ or array icomm has been corrupted.

On entry, n is inconsistent with the value passed to the initialization function: $\mathbf{n}=〈\mathit{\text{value}}〉$, n should be $〈\mathit{\text{value}}〉$.

NE_INTERNAL_ERROR

An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 2.7.6 in How to Use the NAG Library and its Documentation for further information.

NE_NO_LICENCE

Your licence key may have expired or may not have been installed correctly.
See Section 2.7.5 in How to Use the NAG Library and its Documentation for further information.

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example

10.1

Program Text

Program Text (c09cace.c)

10.2

Program Data

Program Data (c09cace.d)

10.3

Program Results

Program Results (c09cace.r)