NAG CL Interface
g03ejc (cluster_​hier_​indicator)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{n}$ – Integer Input

On entry: the number of objects, $n$.

Constraint: $\mathbf{n}\ge 2$.

2: $\mathbf{cd}\left[\mathbf{n}-1\right]$ – const double Input

On entry: the clustering distances in increasing order as returned by g03ecc.

Constraint: $\mathbf{cd}\left[\mathit{i}\right]\ge \mathbf{cd}\left[\mathit{i}-1\right]$, for $\mathit{i}=1,2,\dots ,\mathbf{n}-2$.

3: $\mathbf{iord}\left[\mathbf{n}\right]$ – const Integer Input

On entry: the objects in the dendrogram order as returned by g03ecc.

4: $\mathbf{dord}\left[\mathbf{n}\right]$ – const double Input

On entry: the clustering distances corresponding to the order in iord.

5: $\mathbf{k}$ – Integer * Input/Output

On entry: indicates if a specified number of clusters is required.

$\mathbf{k}>0$

g03ejc will attempt to find k clusters.

$\mathbf{k}\le 0$

g03ejc will find the clusters based on the distance given in dlevel.

Constraint: $\mathbf{k}\le \mathbf{n}$.

On exit: the number of clusters produced, $k$.

6: $\mathbf{dlevel}$ – double * Input/Output

On entry: if $\mathbf{k}\le 0$, then dlevel must contain the distance at which clusters are produced. Otherwise dlevel need not be set.

Constraint: if $\mathbf{k}\le 0$, $\mathbf{dlevel}>0.0$.

On exit: if $\mathbf{k}>0$ on entry, then dlevel contains the distance at which the required number of clusters are found. Otherwise dlevel remains unchanged.

7: $\mathbf{ic}\left[\mathbf{n}\right]$ – Integer Output

On exit: $\mathbf{ic}\left[\mathit{i}-1\right]$ indicates to which of $k$ clusters the $\mathit{i}$th object belongs, for $\mathit{i}=1,2,\dots ,n$.

8: $\mathbf{fail}$ – NagError * Input/Output

The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

NE_2_INT_ARG_GT

On entry, $\mathbf{k}=⟨\mathit{\text{value}}⟩$ while $\mathbf{n}=⟨\mathit{\text{value}}⟩$. These arguments must satisfy $\mathbf{k}\le \mathbf{n}$.

NE_CLUSTER

The precise number of clusters requested is not possible because of
tied clustering distances. The actual number of clusters produced is $⟨\mathit{\text{value}}⟩$.

NE_INCOMP_ARRAYS

Arrays cd and dord are not compatible.

NE_INT_ARG_LT

On entry, $\mathbf{n}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{n}\ge 2$.

NE_INTERNAL_ERROR

An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.

NE_NOT_INCREASING

The sequence cd is not increasing:
$\mathbf{cd}\left[⟨\mathit{\text{value}}⟩\right]=⟨\mathit{\text{value}}⟩$, $\mathbf{cd}\left[⟨\mathit{\text{value}}⟩\right]=⟨\mathit{\text{value}}⟩$.

NE_REAL_INT

On entry, $\mathbf{dlevel}=⟨\mathit{\text{value}}⟩$, $\mathbf{k}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{k}\le 0$ and $\mathbf{dlevel}>0.0$.

NW_2_INT

On exit, $\mathbf{k}=⟨\mathit{\text{value}}⟩$, $\mathbf{n}=⟨\mathit{\text{value}}⟩$.
Trivial solution returned.

NW_INT

On exit, $\mathbf{k}=1$.
Trivial solution returned.

NW_REAL_REALARR

On entry, $\mathbf{dlevel}=⟨\mathit{\text{value}}⟩$, $\mathbf{cd}\left[⟨\mathit{\text{value}}⟩\right]=⟨\mathit{\text{value}}⟩$.
Trivial solution returned.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results