NAG Library Routine Document

M01DAF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     $\mathrm{RV}\left(\mathbf{M2}\right)$ – REAL (KIND=nag_wp) arrayInput

On entry: elements M1 to M2 of RV must contain real values to be ranked.

2:     $\mathrm{M1}$ – INTEGERInput

On entry: the index of the first element of RV to be ranked.

Constraint: $\mathbf{M1}>0$.

3:     $\mathrm{M2}$ – INTEGERInput

On entry: the index of the last element of RV to be ranked.

Constraint: $\mathbf{M2}\ge \mathbf{M1}$.

4:     $\mathrm{ORDER}$ – CHARACTER(1)Input

On entry: if $\mathbf{ORDER}=\text{'A'}$, the values will be ranked in ascending (i.e., nondecreasing) order.

If $\mathbf{ORDER}=\text{'D'}$, into descending order.

Constraint: $\mathbf{ORDER}=\text{'A'}$ or $\text{'D'}$.

5:     $\mathrm{IRANK}\left(\mathbf{M2}\right)$ – INTEGER arrayOutput

On exit: elements M1 to M2 of IRANK contain the ranks of the corresponding elements of RV. Note that the ranks are in the range M1 to M2: thus, if $\mathbf{RV}\left(i\right)$ is the first element in the rank order, $\mathbf{IRANK}\left(i\right)$ is set to M1.

6:     $\mathrm{IFAIL}$ – 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,	$\mathbf{M2}<1$,
or	$\mathbf{M1}<1$,
or	$\mathbf{M1}>\mathbf{M2}$.

$\mathbf{IFAIL}=2$

On entry,

ORDER is not 'A' or 'D'.

$\mathbf{IFAIL}=-99$

An unexpected error has been triggered by this routine. Please contact NAG.

See Section 3.8 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-399$

Your licence key may have expired or may not have been installed correctly.

See Section 3.7 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-999$

Dynamic memory allocation failed.

See Section 3.6 in the Essential Introduction for further information.

7  Accuracy

8  Parallelism and Performance

9  Further Comments

10  Example

10.1  Program Text

Program Text (m01dafe.f90)

10.2  Program Data

Program Data (m01dafe.d)

10.3  Program Results

Program Results (m01dafe.r)