[Scipy-tickets] [SciPy] #1666: LinearNDInterpolator fails when dimensions differ by many orders of magnitude
SciPy Trac
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Sat Jun 2 10:57:57 CDT 2012
#1666: LinearNDInterpolator fails when dimensions differ by many orders of
magnitude
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Reporter: bloop369 | Owner: somebody
Type: defect | Status: new
Priority: normal | Milestone: Unscheduled
Component: scipy.interpolate | Version: 0.10.0
Keywords: LinearNDInterpolator, QHull |
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Comment(by pv):
The scattered data intepolation needs answer to the question "which data
points are close to this one", and this requires a metric. The metric used
in Qhull is ||x-y||_2. Obviously, the results are not affine-invariant
(including scaling). Physically, using such a metric implies that all the
dimensions must have the same units.
Now, your suggestion of making the data axes dimensionless by scaling them
with the range of the data is one possibility, but this may be the wrong
choice in several cases (when the dimensions already have the same units).
I believe the behavior as it is now is correct. AFAIK, it's also how
things work in other numerical packages. This means the user must scale
the data axes before interpolation in a sensible way.
This can be spelled out in more detail in the documentation, and maybe
options could be added to make scaling the data more easily controllable
by the user.
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Ticket URL: <http://projects.scipy.org/scipy/ticket/1666#comment:1>
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