NAG Library Routine Document

M01DJF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     $\mathrm{RM}\left(\mathbf{LDM},\mathbf{N2}\right)$ – REAL (KIND=nag_wp) arrayInput

On entry: rows M1 to M2 of columns N1 to N2 of RM must contain real data to be ranked.

2:     $\mathrm{LDM}$ – INTEGERInput

On entry: the first dimension of the array RM as declared in the (sub)program from which M01DJF is called.

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

3:     $\mathrm{M1}$ – INTEGERInput

On entry: the index of the first row of RM to be used.

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

4:     $\mathrm{M2}$ – INTEGERInput

On entry: the index of the last row of RM to be used.

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

5:     $\mathrm{N1}$ – INTEGERInput

On entry: the index of the first column of RM to be ranked.

Constraint: $\mathbf{N1}>0$.

6:     $\mathrm{N2}$ – INTEGERInput

On entry: the index of the last column of RM to be ranked.

Constraint: $\mathbf{N2}\ge \mathbf{N1}$.

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

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

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

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

8:     $\mathrm{IRANK}\left(\mathbf{N2}\right)$ – INTEGER arrayOutput

On exit: elements N1 to N2 of IRANK contain the ranks of the corresponding columns of RM. Note that the ranks are in the range N1 to N2: thus, if the $i$th column of RM is the first in the rank order, $\mathbf{IRANK}\left(i\right)$ is set to N1.

9:     $\mathrm{IFAIL}$ – 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	$\mathbf{N2}<1$,
or	$\mathbf{M1}<1$,
or	$\mathbf{M1}>\mathbf{M2}$,
or	$\mathbf{N1}<1$,
or	$\mathbf{N1}>\mathbf{N2}$,
or	$\mathbf{LDM}<\mathbf{M2}$.

$\mathbf{IFAIL}=2$

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 (m01djfe.f90)

10.2  Program Data

Program Data (m01djfe.d)

10.3  Program Results

Program Results (m01djfe.r)