NAG Library Routine Document

M01DEF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     RM(LDM,N2) – REAL (KIND=nag_wp) arrayInput

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

2:     LDM – INTEGERInput

On entry: the first dimension of the array RM as declared in the (sub)program from which M01DEF is called.

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

3:     M1 – INTEGERInput

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

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

4:     M2 – INTEGERInput

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

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

5:     N1 – INTEGERInput

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

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

6:     N2 – INTEGERInput

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

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

7:     ORDER – CHARACTER(1)Input

On entry: if $\mathbf{ORDER}=\text{'A'}$, the rows 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:     IRANK(M2) – INTEGER arrayOutput

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

9:     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'.

7  Accuracy

8  Further Comments

9  Example

9.1  Program Text

Program Text (m01defe.f90)

9.2  Program Data

Program Data (m01defe.d)

9.3  Program Results

Program Results (m01defe.r)