NAG Library Function Document

nag_idwt (c09cbc)

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Purpose

2

Specification

3

Description

4

References

5

Arguments

1:    $\mathbf{lenc}$ – IntegerInput

On entry: the dimension of the arrays ca and cd.

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).

2:    $\mathbf{ca}\left[\mathbf{lenc}\right]$ – const doubleInput

On entry: the $n_c$ approximation coefficients, $C_a$. These will normally be the result of some transformation on the coefficients computed by nag_dwt (c09cac).

3:    $\mathbf{cd}\left[\mathbf{lenc}\right]$ – const doubleInput

On entry: the $n_c$ detail coefficients, $C_d$. These will normally be the result of some transformation on the coefficients computed by nag_dwt (c09cac).

4:    $\mathbf{n}$ – IntegerInput

On entry: $n$, the length of the original data array from which the wavelet coefficients were computed by nag_dwt (c09cac) and the length of the data array y that is to be reconstructed by this function.

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

5:    $\mathbf{y}\left[\mathbf{n}\right]$ – doubleOutput

On exit: the reconstructed data based on approximation and detail coefficients $C_a$ and $C_d$ and the transform options supplied to the initialization function nag_wfilt (c09aac).

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

On entry: contains details of the discrete wavelet transform and the problem dimension and, possibly, additional information on the previously computed forward 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.

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Accuracy

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Parallelism and Performance

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Further Comments

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Example