NAG Library Routine Document

C09CBF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     LENC – INTEGERInput

On entry: the dimension of the arrays CA and CD as declared in the (sub)program from which C09CBF is called.

Constraint: $\mathbf{LENC}\ge n_c$, where $n_c$ is the value returned in NWC by the call to the initialization routine C09AAF.

2:     CA(LENC) – REAL (KIND=nag_wp) arrayInput

On entry: the $n_c$ approximation coefficients, $C_a$. These will normally be the result of some transformation on the coefficients computed by C09CAF.

3:     CD(LENC) – REAL (KIND=nag_wp) arrayInput

On entry: the $n_c$ detail coefficients, $C_d$. These will normally be the result of some transformation on the coefficients computed by C09CAF.

4:     N – INTEGERInput

On entry: $n$, the length of the original data array from which the wavelet coefficients were computed by C09CAF and the length of the data array Y that is to be reconstructed by this routine.

Constraint: This must be the same as the value N passed to the initialization routine C09AAF.

5:     Y(N) – REAL (KIND=nag_wp) arrayOutput

On exit: the reconstructed data based on approximation and detail coefficients $C_a$ and $C_d$ and the transform options supplied to the initialization routine C09AAF.

6:     ICOMM($100$) – INTEGER arrayCommunication 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:     IFAIL – INTEGERInput/Output

On entry: IFAIL must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction for details.

For environments where it might be inappropriate to halt program execution when an error is detected, the value $-1\text{ or }1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is $0$. When the value $-\mathbf{1}\text{ or }\mathbf{1}$ is used it is essential to test the value of IFAIL on exit.

On exit: $\mathbf{IFAIL}=\mathbf{0}$ unless the routine detects an error or a warning has been flagged (see Section 6).

6  Error Indicators and Warnings

$\mathbf{IFAIL}=1$

On entry, $\mathbf{LENC}<n_c$, where $n_c$ is the value returned in NWC by the call to the initialization routine C09AAF.

$\mathbf{IFAIL}=4$

On entry, N is inconsistent with the value passed to the initialization routine C09AAF.

$\mathbf{IFAIL}=6$

On entry, the initialization routine C09AAF has not been called first or it has been called with $\mathbf{WTRANS}=\text{'M'}$, or the communication array ICOMM has become corrupted.

7  Accuracy

8  Further Comments

9  Example