def fidw(xs, ds, beta=2):
'''Interpolate using using U{Inverse Distance Weighting
<https://WikiPedia.org/wiki/Inverse_distance_weighting>} (IDW).
@arg xs: Known values (C{scalar}[]).
@arg ds: Non-negative distances (C{scalar}[]).
@kwarg beta: Inverse distance power (C{int}, 0, 1, 2, or 3).
@return: Interpolated value C{x} (C{float}).
@raise ValueError: Invalid B{C{beta}}, negative B{C{ds}} value,
weighted B{C{ds}} below L{EPS} or unequal
C{len}C{(}B{C{ds}}C{)} and C{len}C{(}B{C{xs}}C{)}.
@note: Using B{C{beta}}C{=0} returns the mean of B{C{xs}}.
'''
n, xs = len2(xs)
d, ds = len2(ds)
if n != d or n < 1:
raise LenError(fidw, xs=n, ds=d)
d, x = min(zip(ds, xs))
if d > EPS and n > 1:
b = -Int_(beta, name=_beta_, low=0, high=3)
if b < 0:
ds = tuple(d**b for d in ds)
d = fsum(ds)
if d < EPS:
raise _ValueError(ds=d)
x = fdot(xs, *ds) / d
else:
x = fmean(xs)
elif d < 0:
raise _ValueError(_item_sq('ds', ds.index(d)), d)
return x
def __init__(self, knots, s=4, name=NN):
'''New L{HeightSmoothBiSpline} interpolator.
@arg knots: The points with known height (C{LatLon}s).
@kwarg s: The spline smoothing factor (C{4}).
@kwarg name: Optional name for this height interpolator (C{str}).
@raise HeightError: Insufficient number of B{C{knots}} or
an invalid B{C{knot}} or B{C{s}}.
@raise ImportError: Package C{numpy} or C{scipy} not found
or not installed.
@raise SciPyError: A C{SmoothSphereBivariateSpline} issue.
@raise SciPyWarning: A C{SmoothSphereBivariateSpline} warning
as exception.
'''
_, spi = self._NumSciPy()
s = Int_(s, name='smoothing', Error=HeightError, low=4)
xs, ys, hs = self._xyhs3(knots)
try:
self._ev = spi.SmoothSphereBivariateSpline(ys,
xs,
hs,
eps=EPS,
s=s).ev
except Exception as x:
raise _SciPyIssue(x)
if name:
self.name = name
def beta(self, beta):
'''Set the inverse distance power.
@arg beta: New inverse distance power (C{int} 1, 2, or 3).
@raise HeightError: Invalid B{C{beta}}.
'''
self._beta = Int_(beta, name=_beta_, Error=HeightError, low=1, high=3)
def resolution(prec):
'''Determine the (geographic) resolution of a given L{Garef} precision.
@arg prec: The given precision (C{int}).
@return: The (geographic) resolution (C{degrees}).
@raise GARSError: Invalid B{C{prec}}.
@see: Function L{gars.encode} for more C{precision} details.
'''
p = Int_(prec=prec, Error=GARSError, low=-1, high=_MaxPrec + 1)
return _Resolutions[max(0, min(p, _MaxPrec))]