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Chapter Contents
Chapter Introduction
NAG Toolbox

# NAG Toolbox: nag_file_print_matrix_real_band_comp (x04cf)

## Purpose

nag_file_print_matrix_real_band_comp (x04cf) prints a double band matrix stored in a packed two-dimensional array.

## Syntax

[ifail] = x04cf(m, n, kl, ku, a, form, title, labrow, rlabs, labcol, clabs, ncols, indent)
[ifail] = nag_file_print_matrix_real_band_comp(m, n, kl, ku, a, form, title, labrow, rlabs, labcol, clabs, ncols, indent)

## Description

nag_file_print_matrix_real_band_comp (x04cf) prints a double band matrix stored in a packed two-dimensional array, using a format specifier supplied by you. The matrix is output to the unit defined by nag_file_set_unit_advisory (x04ab).

None.

## Parameters

### Compulsory Input Parameters

1:     $\mathrm{m}$int64int32nag_int scalar
2:     $\mathrm{n}$int64int32nag_int scalar
The number of rows and columns of the band matrix, respectively, to be printed.
If either m or n is less than $1$, nag_file_print_matrix_real_band_comp (x04cf) will exit immediately after printing title; no row or column labels are printed.
3:     $\mathrm{kl}$int64int32nag_int scalar
The number of subdiagonals of the band matrix $A$.
Constraint: ${\mathbf{kl}}\ge 0$.
4:     $\mathrm{ku}$int64int32nag_int scalar
The number of superdiagonals of the band matrix $A$.
Constraint: ${\mathbf{ku}}\ge 0$.
5:     $\mathrm{a}\left(\mathit{lda},:\right)$ – double array
The first dimension of the array a must be at least ${\mathbf{kl}}+{\mathbf{ku}}+1$.
The second dimension of the array a must be at least $\mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,\mathrm{min}\phantom{\rule{0.125em}{0ex}}\left({\mathbf{m}}+{\mathbf{ku}},{\mathbf{n}}\right)\right)$.
The band matrix to be printed.
The matrix is stored in rows $1$ to ${k}_{l}+{k}_{u}+1$, more precisely, the element ${A}_{ij}$ must be stored in
 $aku+1+i-jj for ​max1,j-ku≤i≤minm,j+kl.$
6:     $\mathrm{form}$ – string
Describes the Fortran format code for printing the elements of the matrix a. The format code may be any allowed on the system, whether it is standard Fortran or not. It may or may not be enclosed in brackets.
In addition, there are the following special codes which force nag_file_print_matrix_real_band_comp (x04cf) to choose its own format code:
nag_file_print_matrix_real_band_comp (x04cf) will choose a format code such that numbers will be printed with an F8.4, an F11.4 or a 1PE13.4 format. The F8.4 code is chosen if the sizes of all the matrix elements to be printed lie between $0.001$ and $1.0$. The F11.4 code is chosen if the sizes of all the matrix elements to be printed lie between $0.001$ and $9999.9999$. Otherwise the 1PE13.4 code is chosen.
${\mathbf{form}}=\text{'*'}$
nag_file_print_matrix_real_band_comp (x04cf) will choose a format code such that numbers will be printed to as many significant digits as are necessary to distinguish between neighbouring machine numbers. Thus any two numbers that are stored with different internal representations should look different on output. Whether they do in fact look different will depend on the run-time library of the Fortran compiler in use.
By preceding the desired format code by the string ‘MATLAB’, nag_file_print_matrix_real_band_comp (x04cf) will print the matrix such that it can be input into MATLAB, and title will be used as the name of the matrix.
Examples of valid values for form are $\text{'F11.4'}$, $\text{'1PE13.5'}$, $\text{'G14.5'}$, $\text{'MATLABF11.4'}$, $\text{'MATLAB*'}$.
Constraint: the character length of the format specifier in form must be $\text{}\le 80$.
7:     $\mathrm{title}$ – string
A title to be printed above the matrix, or name of the matrix.
If , no title (and no blank line) will be printed.
If title contains more than ncols characters, the contents of title will be wrapped onto more than one line, with the break after ncols characters.
Any trailing blank characters in title are ignored.
If printing in MATLAB mode, title will be used as the name of the matrix.
8:     $\mathrm{labrow}$ – string (length ≥ 1)
Indicates the type of labelling to be applied to the rows of the matrix, except in MATLAB mode where labrow is ignored.
${\mathbf{labrow}}=\text{'N'}$
Prints no row labels.
${\mathbf{labrow}}=\text{'I'}$
Prints integer row labels.
${\mathbf{labrow}}=\text{'C'}$
Prints character labels, which must be supplied in array rlabs.
Constraint: ${\mathbf{labrow}}=\text{'N'}$, $\text{'I'}$ or $\text{'C'}$.
9:     $\mathrm{rlabs}\left(:\right)$ – cell array of strings
The dimension of the array rlabs must be at least ${\mathbf{m}}$ if ${\mathbf{labrow}}=\text{'C'}$, and at least $1$ otherwise
If ${\mathbf{labrow}}=\text{'C'}$, rlabs must contain labels for the rows of the matrix, except in MATLAB mode where rlabs is ignored.
Labels are right-justified when output, in a field which is as wide as necessary to hold the longest row label. Note that this field width is subtracted from the number of usable columns, ncols.
10:   $\mathrm{labcol}$ – string (length ≥ 1)
Indicates the type of labelling to be applied to the columns of the matrix, except in MATLAB mode where labcol is ignored.
${\mathbf{labcol}}=\text{'N'}$
Prints no column labels.
${\mathbf{labcol}}=\text{'I'}$
Prints integer column labels.
${\mathbf{labcol}}=\text{'C'}$
Prints character labels, which must be supplied in array clabs.
Constraint: ${\mathbf{labcol}}=\text{'N'}$, $\text{'I'}$ or $\text{'C'}$.
11:   $\mathrm{clabs}\left(:\right)$ – cell array of strings
The dimension of the array clabs must be at least ${\mathbf{n}}$ if ${\mathbf{labcol}}=\text{'C'}$, and at least $1$ otherwise
If ${\mathbf{labcol}}=\text{'C'}$, clabs must contain labels for the columns of the matrix, except in MATLAB mode where clabs is ignored.
Labels are right-justified when output. Any label that is too long for the column width, which is determined by form, is truncated.
12:   $\mathrm{ncols}$int64int32nag_int scalar
The maximum output record length. If the number of columns of the matrix is too large to be accommodated in ncols characters, the matrix will be printed in parts, containing the largest possible number of matrix columns, and each part separated by a blank line.
ncols must be large enough to hold at least one column of the matrix using the format specifier in form. If a value less than 0 or greater than $132$ is supplied for ncols, then the value $80$ is used instead.
13:   $\mathrm{indent}$int64int32nag_int scalar
The number of columns by which the matrix (and any title and labels) should be indented. The effective value of ncols is reduced by indent columns. If a value less than $0$ or greater than ncols is supplied for indent, the value $0$ is used instead.

None.

### Output Parameters

1:     $\mathrm{ifail}$int64int32nag_int scalar
${\mathbf{ifail}}={\mathbf{0}}$ unless the function detects an error (see Error Indicators and Warnings).

## Error Indicators and Warnings

Errors or warnings detected by the function:
${\mathbf{ifail}}=1$
 On entry, ${\mathbf{kl}}<0$.
${\mathbf{ifail}}=2$
 On entry, ${\mathbf{ku}}<0$.
${\mathbf{ifail}}=3$
 On entry, $\mathit{lda}<{\mathbf{kl}}+{\mathbf{ku}}+1$.
${\mathbf{ifail}}=4$
 On entry, the format specifier in form is more than $80$ characters long.
${\mathbf{ifail}}=5$
The format specifier in form cannot be used to output a number. The specifier probably has too wide a field width or contains an illegal edit descriptor.
${\mathbf{ifail}}=6$
 On entry, either labrow or ${\mathbf{labcol}}\ne \text{'N'}$, $\text{'I'}$ or $\text{'C'}$.
${\mathbf{ifail}}=7$
The quantity ${\mathbf{ncols}}-{\mathbf{indent}}-\mathit{labwid}$ (where $\mathit{labwid}$ is the width needed for the row labels) is not large enough to hold at least one column of the matrix.
${\mathbf{ifail}}=-99$
${\mathbf{ifail}}=-399$
Your licence key may have expired or may not have been installed correctly.
${\mathbf{ifail}}=-999$
Dynamic memory allocation failed.

Not applicable.

None.

## Example

This example calls nag_file_print_matrix_real_band_comp (x04cf) three times, to print $5$ by $5$ matrices of different bandwidths; various options for labelling and formatting are illustrated.
```function x04cf_example

fprintf('x04cf example results\n\n');

m = int64(5);
n = int64(5);

% First Example: tridiagonal matrix A
mtitle  = 'Example 1:';
kl = int64(1);
ku = int64(1);
a = [ 0, 12, 13, 14, 15;
21, 22, 23, 24, 25;
31, 32, 33, 34,  0];

% Default format
format = ' ';

% Integer labels
labrow = 'Integer';
labcol = labrow;
rlabs  = {'       '};
clabs  = {'       '};

% 80 columns wide, no indent
ncols  = int64(80);
indent = int64(0);

[ifail] = x04cf( ...
m, n, kl, ku, a, format, mtitle, labrow, ...
rlabs, labcol, clabs, ncols, indent);

fprintf('\n');
% First Example: 2 Super-diagonals + 1 sub-diagonal
mtitle  = 'Example 2:';
kl = int64(1);
ku = int64(2);
a = [ 0,  0, 13, 14, 15;
0, 22, 23, 24, 25;
31, 32, 33, 34, 35;
41, 42, 43, 44,  0];

% '%8.2f' style format
format = 'F8.2';

% Character labels
labrow = 'Character';
labcol = labrow;
rlabs  = {'Uno    '; 'Due    '; 'Tre    '; 'Quattro'; 'Cinque '};
clabs  = {'Un     '; 'Deux   '; 'Trois  '; 'Quatre '; 'Cinq   '};

[ifail] = x04cf( ...
m, n, kl, ku, a, format, mtitle, labrow, ...
rlabs, labcol, clabs, ncols, indent);

fprintf('\n Example 3:\n');
% Third matrix: As above but printed in Matlab form
mtitle = 'A';
format = 'MATLABF8.2';
labrow = 'No labels';
labcol = labrow;

[ifail] = x04cf( ...
m, n, kl, ku, a, format, mtitle, labrow, ...
rlabs, labcol, clabs, ncols, indent);

```
```x04cf example results

Example 1:
1          2          3          4          5
1     21.0000    12.0000
2     31.0000    22.0000    13.0000
3                32.0000    23.0000    14.0000
4                           33.0000    24.0000    15.0000
5                                      34.0000    25.0000

Example 2:
Un    Deux   Trois  Quatre    Cinq
Uno    31.00   22.00   13.00
Due    41.00   32.00   23.00   14.00
Tre            42.00   33.00   24.00   15.00
Quattro                    43.00   34.00   25.00
Cinque                            44.00   35.00

Example 3:
A = [
31.00   22.00   13.00    0.00    0.00;
41.00   32.00   23.00   14.00    0.00;
0.00   42.00   33.00   24.00   15.00;
0.00    0.00   43.00   34.00   25.00;
0.00    0.00    0.00   44.00   35.00;
];
```