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X04 Chapter Introduction
NAG Library Manual

# NAG Library Routine DocumentX04EAF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

## 1  Purpose

X04EAF is an easy-to-use routine to print an integer matrix stored in a two-dimensional array.

## 2  Specification

 SUBROUTINE X04EAF ( MATRIX, DIAG, M, N, A, LDA, TITLE, IFAIL)
 INTEGER M, N, A(LDA,*), LDA, IFAIL CHARACTER(*) TITLE CHARACTER(1) MATRIX, DIAG

## 3  Description

X04EAF prints an integer matrix. It is an easy-to-use driver for X04EBF. The routine uses default values for the format in which numbers are printed, for labelling the rows and columns, and for output record length.
X04EAF will choose a format code such that numbers will be printed with the smallest I edit descriptor that is large enough to hold all the numbers to be printed.
The matrix is printed with integer row and column labels, and with a maximum record length of $80$.
The matrix is output to the unit defined by X04ABF.

None.

## 5  Parameters

1:     MATRIX – CHARACTER(1)Input
On entry: indicates the part of the matrix to be printed.
${\mathbf{MATRIX}}=\text{'G'}$
The whole of the rectangular matrix.
${\mathbf{MATRIX}}=\text{'L'}$
The lower triangle of the matrix, or the lower trapezium if the matrix has more rows than columns.
${\mathbf{MATRIX}}=\text{'U'}$
The upper triangle of the matrix, or the upper trapezium if the matrix has more columns than rows.
Constraint: ${\mathbf{MATRIX}}=\text{'G'}$, $\text{'L'}$ or $\text{'U'}$.
2:     DIAG – CHARACTER(1)Input
On entry: unless ${\mathbf{MATRIX}}=\text{'G'}$, DIAG must specify whether the diagonal elements of the matrix are to be printed.
${\mathbf{DIAG}}=\text{'B'}$
The diagonal elements of the matrix are not referenced and not printed.
${\mathbf{DIAG}}=\text{'U'}$
The diagonal elements of the matrix are not referenced, but are assumed all to be unity, and are printed as such.
${\mathbf{DIAG}}=\text{'N'}$
The diagonal elements of the matrix are referenced and printed.
If ${\mathbf{MATRIX}}=\text{'G'}$, then DIAG need not be set.
Constraint: if ${\mathbf{MATRIX}}\ne \text{'G'}$, ${\mathbf{DIAG}}=\text{'B'}$, $\text{'U'}$ or $\text{'N'}$.
3:     M – INTEGERInput
4:     N – INTEGERInput
On entry: the number of rows and columns of the matrix, respectively, to be printed.
If either M or N is less than $1$, X04EAF will exit immediately after printing TITLE; no row or column labels are printed.
5:     A(LDA,$*$) – INTEGER arrayInput
Note: the second dimension of the array A must be at least $\mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,{\mathbf{N}}\right)$.
On entry: the matrix to be printed. Only the elements that will be referred to, as specified by parameters MATRIX and DIAG, need be set.
6:     LDA – INTEGERInput
On entry: the first dimension of the array A as declared in the (sub)program from which X04EAF is called.
Constraint: ${\mathbf{LDA}}\ge \mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,{\mathbf{M}}\right)$.
7:     TITLE – CHARACTER(*)Input
On entry: a title to be printed above the matrix.
If , no title (and no blank line) will be printed.
If TITLE contains more than $80$ characters, the contents of TITLE will be wrapped onto more than one line, with the break after $80$ characters.
Any trailing blank characters in TITLE are ignored.
8:     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

If on entry ${\mathbf{IFAIL}}={\mathbf{0}}$ or $-{\mathbf{1}}$, explanatory error messages are output on the current error message unit (as defined by X04AAF).
Errors or warnings detected by the routine:
${\mathbf{IFAIL}}=1$
 On entry, ${\mathbf{MATRIX}}\ne \text{'G'}$, $\text{'L'}$ or $\text{'U'}$.
${\mathbf{IFAIL}}=2$
 On entry, ${\mathbf{MATRIX}}=\text{'L'}$ or $\text{'U'}$, but ${\mathbf{DIAG}}\ne \text{'N'}$, $\text{'U'}$ or $\text{'B'}$.
${\mathbf{IFAIL}}=3$
 On entry, ${\mathbf{LDA}}<{\mathbf{M}}$.

## 7  Accuracy

Not applicable.

A call to X04EAF is equivalent to a call to X04EBF with the following argument values:
```
NCOLS = 80
INDENT = 0
LABROW = 'I'
LABCOL = 'I'
FORM = ' '

```

## 9  Example

This example calls X04EAF twice, first to print a $3$ by $5$ rectangular matrix, and then to print a $5$ by $5$ triangular matrix.

### 9.1  Program Text

Program Text (x04eafe.f90)

None.

### 9.3  Program Results

Program Results (x04eafe.r)