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DM-33530: Spline fitter fails when insufficient length array input #207

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Feb 7, 2022
Merged

DM-33530: Spline fitter fails when insufficient length array input #207

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306b9ba
Identify spline fit problems, work around them, but mask the amplifier.
czwa Feb 2, 2022
a5b8e22
Akima splines need 5 points.
czwa Feb 3, 2022
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26 changes: 24 additions & 2 deletions python/lsst/ip/isr/overscan.py
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Original file line number Diff line number Diff line change
Expand Up @@ -382,6 +382,18 @@ def splineFit(self, indices, collapsed, numBins):
weights=collapsed.data*~collapsed.mask)[0]/numPerBin
binCenters = np.histogram(indices, bins=numBins,
weights=indices*~collapsed.mask)[0]/numPerBin

if len(binCenters[numPerBin > 0]) < 5:
self.log.warn("Cannot do spline fitting for overscan: %s valid points.",
len(binCenters[numPerBin > 0]))
# Return a scalar value if we have one, otherwise
# return zero. This amplifier is hopefully already
# masked.
if len(values[numPerBin > 0]) != 0:
return float(values[numPerBin > 0][0])
else:
return 0.0

interp = afwMath.makeInterpolate(binCenters.astype(float)[numPerBin > 0],
values.astype(float)[numPerBin > 0],
afwMath.stringToInterpStyle(self.config.fitType))
Expand Down Expand Up @@ -482,9 +494,19 @@ def measureVectorOverscan(self, image):
'AKIMA_SPLINE': (self.splineFit, self.splineEval)
}[self.config.fitType]

# These are the polynomial coefficients, or an
# interpolation object.
coeffs = fitter(indices, collapsed, self.config.order)
overscanVector = evaler(indices, coeffs)
maskArray = self.maskExtrapolated(collapsed)

if isinstance(coeffs, float):
self.log.warn("Using fallback value %f due to fitter failure. Amplifier will be masked.",
coeffs)
overscanVector = np.full_like(indices, coeffs)
maskArray = np.full_like(collapsed, True, dtype=bool)
else:
# Otherwise we can just use things as normal.
overscanVector = evaler(indices, coeffs)
maskArray = self.maskExtrapolated(collapsed)
return pipeBase.Struct(overscanValue=np.array(overscanVector),
maskArray=maskArray,
isTransposed=isTransposed)
Expand Down