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# NAG Toolbox: nag_file_print_matrix_real_packed_comp (x04cd)

## Purpose

nag_file_print_matrix_real_packed_comp (x04cd) prints a double triangular matrix stored in a packed one-dimensional array.

## Syntax

[ifail] = x04cd(uplo, diag, n, a, form, title, labrow, rlabs, labcol, clabs, ncols, indent)
[ifail] = nag_file_print_matrix_real_packed_comp(uplo, diag, n, a, form, title, labrow, rlabs, labcol, clabs, ncols, indent)

## Description

nag_file_print_matrix_real_packed_comp (x04cd) prints a double triangular matrix stored in packed form, using a format specifier supplied by you. The matrix must be packed by column. The matrix is output to the unit defined by nag_file_set_unit_advisory (x04ab).

None.

## Parameters

### Compulsory Input Parameters

1:     uplo – string (length ≥ 1)
Indicates the type of the matrix to be printed
uplo = 'L'${\mathbf{uplo}}=\text{'L'}$
The matrix is lower triangular. In this case, the packed array a holds the matrix elements in the following order: (1,1),(2,1),,(n,1),(2,2),(3,2),,(n,2)$\left(1,1\right),\left(2,1\right),\dots ,\left({\mathbf{n}},1\right),\left(2,2\right),\left(3,2\right),\dots ,\left({\mathbf{n}},2\right)$, etc.
uplo = 'U'${\mathbf{uplo}}=\text{'U'}$
The matrix is upper triangular. In this case, the packed array a holds the matrix elements in the following order: (1,1),(1,2),(2,2),(1,3),(2,3),(3,3),(1,4)$\left(1,1\right),\left(1,2\right),\left(2,2\right),\left(1,3\right),\left(2,3\right),\left(3,3\right),\left(1,4\right)$, etc.
Constraint: uplo = 'L'${\mathbf{uplo}}=\text{'L'}$ or 'U'$\text{'U'}$.
2:     diag – string (length ≥ 1)
Indicates whether the diagonal elements of the matrix are to be printed.
diag = 'B'${\mathbf{diag}}=\text{'B'}$
The diagonal elements of the matrix are not referenced and not printed.
diag = 'U'${\mathbf{diag}}=\text{'U'}$
The diagonal elements of the matrix are not referenced, but are assumed all to be unity, and are printed as such.
diag = 'N'${\mathbf{diag}}=\text{'N'}$
The diagonal elements of the matrix are referenced and printed.
Constraint: diag = 'B'${\mathbf{diag}}=\text{'B'}$, 'U'$\text{'U'}$ or 'N'$\text{'N'}$.
3:     n – int64int32nag_int scalar
The order of the matrix to be printed.
If n is less than 1$1$, nag_file_print_matrix_real_packed_comp (x04cd) will exit immediately after printing title; no row or column labels are printed.
4:     a( : $:$) – double array
Note: the dimension of the array a must be at least max (1,n × (n + 1) / 2)$\mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,{\mathbf{n}}×\left({\mathbf{n}}+1\right)/2\right)$.
The matrix to be printed. Note that a must have space for the diagonal elements of the matrix, even if these are not stored.
More precisely,
• if uplo = 'U'${\mathbf{uplo}}=\text{'U'}$, the upper triangle of A$A$ must be stored with element Aij${A}_{ij}$ in a(i + j(j1) / 2)${\mathbf{a}}\left(i+j\left(j-1\right)/2\right)$ for ij$i\le j$;
• if uplo = 'L'${\mathbf{uplo}}=\text{'L'}$, the lower triangle of A$A$ must be stored with element Aij${A}_{ij}$ in a(i + (2nj)(j1) / 2)${\mathbf{a}}\left(i+\left(2n-j\right)\left(j-1\right)/2\right)$ for ij$i\ge j$.
If diag = 'U'${\mathbf{diag}}=\text{'U'}$, the diagonal elements of A$A$ are assumed to be 1$1$, and are not referenced; the same storage scheme is used whether diag = 'N'${\mathbf{diag}}=\text{'N'}$ or ‘U’.
5:     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_packed_comp (x04cd) to choose its own format code:
form = ' '
nag_file_print_matrix_real_packed_comp (x04cd) 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$0.001$ and 1.0$1.0$. The F11.4 code is chosen if the sizes of all the matrix elements to be printed lie between 0.001$0.001$ and 9999.9999$9999.9999$. Otherwise the 1PE13.4 code is chosen.
form = '*'${\mathbf{form}}=\text{'*'}$
nag_file_print_matrix_real_packed_comp (x04cd) 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_packed_comp (x04cd) 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 'F11.4'$\text{'F11.4'}$, '1PE13.5'$\text{'1PE13.5'}$, 'G14.5'$\text{'G14.5'}$, 'MATLABF11.4'$\text{'MATLABF11.4'}$, 'MATLAB*'$\text{'MATLAB*'}$.
Constraint: the character length of the format specifier in form must be 80$\text{}\le 80$.
6:     title – string
A title to be printed above the matrix, or name of the matrix.
If title = ' ', 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.
7:     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.
labrow = 'N'${\mathbf{labrow}}=\text{'N'}$
Prints no row labels.
labrow = 'I'${\mathbf{labrow}}=\text{'I'}$
Prints integer row labels.
labrow = 'C'${\mathbf{labrow}}=\text{'C'}$
Prints character labels, which must be supplied in array rlabs.
Constraint: labrow = 'N'${\mathbf{labrow}}=\text{'N'}$, 'I'$\text{'I'}$ or 'C'$\text{'C'}$.
8:     rlabs( : $:$) – cell array of strings
Note: the dimension of the array rlabs must be at least n${\mathbf{n}}$ if labrow = 'C'${\mathbf{labrow}}=\text{'C'}$, and at least 1$1$ otherwise.
If labrow = 'C'${\mathbf{labrow}}=\text{'C'}$, 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.
9:     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.
labcol = 'N'${\mathbf{labcol}}=\text{'N'}$
Prints no column labels.
labcol = 'I'${\mathbf{labcol}}=\text{'I'}$
Prints integer column labels.
labcol = 'C'${\mathbf{labcol}}=\text{'C'}$
Prints character labels, which must be supplied in array clabs.
Constraint: labcol = 'N'${\mathbf{labcol}}=\text{'N'}$, 'I'$\text{'I'}$ or 'C'$\text{'C'}$.
10:   clabs( : $:$) – cell array of strings
Note: the dimension of the array clabs must be at least n${\mathbf{n}}$ if labcol = 'C'${\mathbf{labcol}}=\text{'C'}$, and at least 1$1$ otherwise.
If labcol = 'C'${\mathbf{labcol}}=\text{'C'}$, 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.
11:   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$132$ is supplied for ncols, then the value 80$80$ is used instead.
12:   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$0$ or greater than ncols is supplied for indent, the value 0$0$ is used instead.

None.

None.

### Output Parameters

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

## Error Indicators and Warnings

Errors or warnings detected by the function:
ifail = 1${\mathbf{ifail}}=1$
 On entry, uplo ≠ 'L'${\mathbf{uplo}}\ne \text{'L'}$ or 'U'$\text{'U'}$.
ifail = 2${\mathbf{ifail}}=2$
 On entry, diag ≠ 'N'${\mathbf{diag}}\ne \text{'N'}$, 'U'$\text{'U'}$ or 'B'$\text{'B'}$.
ifail = 3${\mathbf{ifail}}=3$
 On entry, the format specifier in form is more than 80$80$ characters long.
ifail = 4${\mathbf{ifail}}=4$
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.
ifail = 5${\mathbf{ifail}}=5$
 On entry, either labrow or labcol ≠ 'N'${\mathbf{labcol}}\ne \text{'N'}$, 'I'$\text{'I'}$ or 'C'$\text{'C'}$.
ifail = 6${\mathbf{ifail}}=6$
The quantity ncolsindentlabwid${\mathbf{ncols}}-{\mathbf{indent}}-\mathit{labwid}$ (where labwid$\mathit{labwid}$ is the width needed for the row labels) is not large enough to hold at least one column of the matrix.

Not applicable.

None.

## Example

```function nag_file_print_matrix_real_packed_comp_example
uplo = 'Lower';
diag = 'Non-unit';
n = int64(4);
a = [1;2;3;4;5;6;7;8;9;10];
format = ' ';
title = 'Example 1:';
labrow = 'Integer';
rlabs = {'Uno    '};
labcol = 'Integer';
clabs = {'Un     '};
ncols = int64(80);
indent = int64(0);
[ifail] = ...
nag_file_print_matrix_real_packed_comp(uplo, diag, n, a, format, title, ...
labrow, rlabs, labcol, clabs, ncols, indent)
```
```
Example 1:
1          2          3          4
1      1.0000
2      2.0000     5.0000
3      3.0000     6.0000     8.0000
4      4.0000     7.0000     9.0000    10.0000

ifail =

0

```
```function x04cd_example
uplo = 'Lower';
diag = 'Non-unit';
n = int64(4);
a = [1;2;3;4;5;6;7;8;9;10];
format = ' ';
title = 'Example 1:';
labrow = 'Integer';
rlabs = {'Uno    '};
labcol = 'Integer';
clabs = {'Un     '};
ncols = int64(80);
indent = int64(0);
[ifail] = ...
x04cd(uplo, diag, n, a, format, title, labrow, rlabs, labcol, clabs, ...
ncols, indent)
```
```
Example 1:
1          2          3          4
1      1.0000
2      2.0000     5.0000
3      3.0000     6.0000     8.0000
4      4.0000     7.0000     9.0000    10.0000

ifail =

0

```

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