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MGH_SUBSET

MGH_SUBSET

## Purpose

Given a 1D monotonic vector (xin) representing location, and a pair of
positions (bound), this function returns the indices into the vector that
bracket those positions.
This function addresses a very common situation: we have a vector
representing (say) longitude for a global dataset and we wish
to draw out a subset of the data.
If xin is increasing (decreasing) then it is expected that bound[1] will
be greater (less) than or equal to bound[0].

## Calling Sequence

Result = MGH_SUBSET(xin, bound)

## Positional Parameters

xin (input, 1-D numeric array)
X positions of the vertices of the input grid. The X values
should be monotonic (if not, results will be unpredictable);
they need not be uniform.
bound (input, 2-element numeric array)
The boundaries of the subset in the position space defined by xin.
If the first (second) element of bound is non-finite, then the
corresponding result will be 0 (n_elements(xin)-1).

## Keyword Parameters

EMPTY (output, logical scalar)
Set this keyword to a named variable to return a logical value
indicating whether the range is empty.
ROUND (input, integer scalar)
This keyword determines whether we search for a subset that
either matches the range as closely as possible (round eq 0)
exceeds the range (round gt 0) or fits inside the range (round lt 0)

## Return Value

The function returns a 2-element integer vector representing the range
of indices.

## Procedure

Locate the end points via MGH_LOCATE, then round up or down as necessary.
Clip so that the result represents a valid range of indices.
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accuracy of the software, the use to which the software may
be put or the results to be obtained from the use of the
software. Accordingly NIWA accepts no liability for any loss
or damage (whether direct of indirect) incurred by any person
through the use of or reliance on the software.
2. NIWA is to be acknowledged as the original author of the
software where the software is used or presented in any form.
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Written.