NAG Library Routine Document

G03EHF

1  Purpose

2  Specification

3  Description

Figure 1

4  References

5  Parameters

1:     ORIENT – CHARACTER(1)Input

On entry: indicates which orientation the dendrogram is to take.

$\mathbf{ORIENT}=\text{'N'}$

The end points of the dendrogram are to the north.

$\mathbf{ORIENT}=\text{'S'}$

The end points of the dendrogram are to the south.

$\mathbf{ORIENT}=\text{'E'}$

The end points of the dendrogram are to the east.

$\mathbf{ORIENT}=\text{'W'}$

The end points of the dendrogram are to the west.

Constraint: $\mathbf{ORIENT}=\text{'N'}$, $\text{'S'}$, $\text{'E'}$ or $\text{'W'}$.

2:     N – INTEGERInput

On entry: the number of objects in the cluster analysis.

Constraint: $\mathbf{N}>2$.

3:     DORD(N) – REAL (KIND=nag_wp) arrayInput

On entry: the array DORD as output by G03ECF. DORD contains the distances, in dendrogram order, at which clustering takes place.

Constraint: $\mathbf{DORD}\left(\mathbf{N}\right)\ge \mathbf{DORD}\left(\mathit{i}\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{N}-1$.

4:     DMIN – REAL (KIND=nag_wp)Input

On entry: the clustering distance at which the dendrogram begins.

Constraint: $\mathbf{DMIN}\ge 0.0$.

5:     DSTEP – REAL (KIND=nag_wp)Input

On entry: the distance represented by one symbol of the dendrogram.

Constraint: $\mathbf{DSTEP}>0.0$.

6:     NSYM – INTEGERInput

On entry: the number of character positions used in the dendrogram. Hence the clustering distance at which the dendrogram terminates is given by $\mathbf{DMIN}+\mathbf{NSYM}\times \mathbf{DSTEP}$.

Constraint: $\mathbf{NSYM}\ge 1$.

7:     C(LENC) – CHARACTER(*) arrayOutput

Note:  the length of each element of C must be at least $3\times \mathbf{N}$ if $\mathbf{ORIENT}=\text{'N'}$ or $\text{'S'}$, or at least NSYM if $\mathbf{ORIENT}=\text{'E'}$ or $\text{'W'}$.

On exit: the elements of C contain consecutive lines of the dendrogram.

8:     LENC – INTEGERInput

On entry: the dimension of the array C as declared in the (sub)program from which G03EHF is called.

Constraints:

• if $\mathbf{ORIENT}=\text{'N'}$ or $\text{'S'}$, $\mathbf{LENC}\ge \mathbf{NSYM}$;
• if $\mathbf{ORIENT}=\text{'E'}$ or $\text{'W'}$, $\mathbf{LENC}\ge \mathbf{N}$.

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,	$\mathbf{N}\le 2$,
or	$\mathbf{NSYM}<1$,
or	$\mathbf{DMIN}<0.0$,
or	$\mathbf{DSTEP}\le 0.0$,
or	$\mathbf{ORIENT}\ne \text{'N'},\text{'S'},\text{'E'}$, or 'W',
or	$\mathbf{ORIENT}=\text{'N'}$ or $\text{'S'}$, $\mathbf{LENC}<\mathbf{NSYM}$,
or	$\mathbf{ORIENT}=\text{'E'}$ or $\text{'W'}$, $\mathbf{LENC}<\mathbf{N}$,
or	the number of characters that can be stored in each element of array C is insufficient for the requested orientation.

$\mathbf{IFAIL}=2$

On entry,

$\mathbf{DORD}\left(\mathbf{N}\right)<\mathbf{DORD}\left(i\right)$, for some $i=1,2,\dots ,\mathbf{N}-1$.

7  Accuracy

8  Further Comments

9  Example

9.1  Program Text

Program Text (g03ehfe.f90)

9.2  Program Data

Program Data (g03ehfe.d)

9.3  Program Results

Program Results (g03ehfe.r)