nag_file_print_matrix_real_band (x04ce) prints a double band matrix stored in a packed two-dimensional array. It is an easy-to-use driver for nag_file_print_matrix_real_band_comp (x04cf). The function uses default values for the format in which numbers are printed, for labelling the rows and columns, and for output record length.

nag_file_print_matrix_real_band (x04ce) will choose a format code such that numbers will be printed with an

F 8.4

, an

F 11.4

or a

1 PE 13.4

format . The

F 8.4

code is chosen if the sizes of all the matrix elements to be printed lie between

0.001

and

1.0

. The

F 11.4

code is chosen if the sizes of all the matrix elements to be printed lie between

0.001

and

9999.9999

. Otherwise the

1 PE 13.4

code is chosen.

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 nag_file_set_unit_advisory (x04ab).

References

None.

Parameters

Compulsory Input Parameters

1: $m$ – int64int32nag_int scalar

2: $n$ – 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 (x04ce) will exit immediately after printing title; no row or column labels are printed.

3: $kl$ – int64int32nag_int scalar

The number of subdiagonals of the band matrix

A

Constraint:

kl \geq 0

4: $ku$ – int64int32nag_int scalar

The number of superdiagonals of the band matrix

A

Constraint:

ku \geq 0

5: $a (lda :)$ – double array

The first dimension of the array a must be at least

kl + ku + 1

The second dimension of the array a must be at least

\max (1, \min (m + ku, n))

The band matrix to be printed.

The matrix is stored in rows

1

k_{l} + k_{u} + 1

, more precisely, the element

A_{i j}

must be stored in

a (k_{u} + 1 + i - j, j) for ​ \max (1, j - k_{u}) \leq i \leq \min (m, j + k_{l}) .

6: $title$ – string

A title to be printed above the matrix.

title =' '

, 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.

Optional Input Parameters

None.

Output Parameters

1: $ifail$ – int64int32nag_int scalar: $ifail = 0$ unless the function detects an error (see Error Indicators and Warnings).

Error Indicators and Warnings

Errors or warnings detected by the function:

$ifail = 1$

On entry,

kl < 0

$ifail = 2$

On entry,

ku < 0

$ifail = 3$

On entry,

lda < kl + ku + 1

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.

$ifail = - 399$: Your licence key may have expired or may not have been installed correctly.

$ifail = - 999$: Dynamic memory allocation failed.

Accuracy

Not applicable.

Further Comments

A call to nag_file_print_matrix_real_band (x04ce) is equivalent to a call to nag_file_print_matrix_real_band_comp (x04cf) with the following argument values:


ncols = 80
indent = 0
labrow = 'I'
labcol = 'I'
form = ' '

Example

The example program calls nag_file_print_matrix_real_band (x04ce) to print a

5

5

band matrix with one subdiagonal and one superdiagonal.

Open in the MATLAB editor: x04ce_example

function x04ce_example


fprintf('x04ce example results\n\n');

% Banded matrix (tridiagonal) A in banded storage format
m  = int64(5);
n  = m;
kl = int64(1);
ku = kl;
% diagonals are stored as rows and columns are preserved.
a  = [ 0, 12, 13, 14, 15;
      21, 22, 23, 24, 25;
      31, 32, 33, 34,  0];

mtitle = 'Band Matrix:';
[ifail] = x04ce(m, n, kl, ku, a, mtitle);

x04ce example results

 Band Matrix:
             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

PDF version (NAG web site, 64-bit version, 64-bit version)

Chapter Contents

Chapter Introduction

NAG Toolbox