VALUE_LOCATE locates the positions of given values within a
reference array. The reference array need not be regularly
spaced. This is useful for various searching, sorting and
interpolation algorithms.
The reference array should be a monotonically increasing or
decreasing list of values which partition the real numbers. A
reference array of NBINS numbers partitions the real number line
into NBINS+1 regions, like so:
REF: X[0] X[1] X[2] X[3] X[NBINS-1]
<----------|-------------|------|---|----...---|--------------->
INDICES: -1 0 1 2 3 NBINS-1
VALUE_LOCATE returns which partition each of the VALUES falls
into, according to the figure above. For example, a value between
X[1] and X[2] would return a value of 1. Values below X[0] return
-1, and above X[NBINS-1] return NBINS-1. Thus, besides the value
of -1, the returned INDICES refer to the nearest reference value
to the left of the requested value.
Example:
>>> refx = [2, 4, 6, 8, 10]
>>> x = [-1, 1, 2, 3, 5, 5, 5, 8, 12, 30]
>>> print value_locate(refx, x)
array([-1, -1, 0, 0, 1, 1, 1, 3, 4, 4])
This implementation is likely no the most efficient one, as there is
a loop over all x, which will in practice be long. As long as x is
shorter than 1e6 or so elements, it should still be fast (~sec).
Definition at line 11 of file value_locate.py.
