naginterfaces.library.sort.charvec_​rank

naginterfaces.library.sort.charvec_rank(ch, m1, l1, l2, order)

charvec_rank ranks a vector of character data in ASCII or reverse ASCII order of a specified substring.

For full information please refer to the NAG Library document for m01dc

https://support.nag.com/numeric/nl/nagdoc_30/flhtml/m01/m01dcf.html

Parameters

chstr, array-like, shape $\left(\text{m2}\right)$

Elements $m1-1$ to $\text{m2}-1$ of $ch$ must contain character data to be ranked.

m1int

Note: this argument represents an array index; the value you supply must be base-1 for compatibility with the NAG Engine.

The index of the first element of $ch$ to be ranked.

l1int

Only the substring ($l1$:$l2$) of each element of $ch$ is to be used in determining the rank order.

l2int

Only the substring ($l1$:$l2$) of each element of $ch$ is to be used in determining the rank order.

orderstr, length 1

If $order=\text{'A'}$, the values will be ranked in ASCII order.

If $order=\text{'R'}$, in reverse ASCII order.

Returns

irankint, ndarray, shape $\left(\text{m2}\right)$

Elements $m1-1$ to $\text{m2}-1$ of $irank$ contain the ranks of the corresponding elements of $ch$. Note that the ranks are in the range $m1$ to $\text{m2}$: thus, if $ch[i-1]$ is the first element in the rank order, $irank[i-1]$ is set to $m1$.

Raises

NagValueError

(errno $1$)

On entry, $l2=⟨value⟩$ and $len\left(ch\right[0\left]\right)=⟨value⟩$.

Constraint: $l2\le len\left(ch\right[0\left]\right)$.

(errno $1$)

On entry, $l1=⟨value⟩$ and $l2=⟨value⟩$.

Constraint: $l1\le l2$.

(errno $1$)

On entry, $l1=⟨value⟩$.

Constraint: $l1\ge 1$.

(errno $1$)

On entry, $l2=⟨value⟩$.

Constraint: $l2\ge 1$.

(errno $1$)

On entry, $m1=⟨value⟩$ and $\text{m2}=⟨value⟩$.

Constraint: $m1\le \text{m2}$.

(errno $1$)

On entry, $m1=⟨value⟩$.

Constraint: $m1\ge 1$.

(errno $1$)

On entry, $\text{m2}=⟨value⟩$.

Constraint: $\text{m2}\ge 1$.

(errno $2$)

On entry, $order$ has an illegal value: $order=⟨value⟩$.

(errno $3$)

On entry, $len\left(ch\right[0\left]\right)=⟨value⟩$.

Constraint: $len\left(ch\right[0\left]\right)\le 255$.

Notes

No equivalent traditional C interface for this routine exists in the NAG Library.

charvec_rank uses a variant of list-merging, as described on pages 165–166 in Knuth (1973). The function takes advantage of natural ordering in the data, and uses a simple list insertion in a preparatory pass to generate ordered lists of length at least $10$. The ranking is stable: equal elements preserve their ordering in the input data.

Only the substring ($l1$:$l2$) of each element of the array $ch$ is used to determine the rank order.

References

Knuth, D E, 1973, The Art of Computer Programming (Volume 3), (2nd Edition), Addison–Wesley