LinearitySolveTask¶

LinearitySolveTask constructs a linearity correction model (a Linearizer) based on the results stored in the input photon transfer curve (PTC) dataset.

Processing summary¶

LinearitySolveTask runs these operations:

Convert the input exposure time/photodiode flux measurement to a proxy flux by fitting the low-flux end with a linear fit.
Perform fit against using the observed flux and this linear proxy flux (using either a spline or a polynomial).
Store the correction, such that the corrected flux is equal to the uncorrected flux + the linearity correction as a function of the uncorrected flux.

Python API summary¶

from lsst.cp.pipe.linearity import LinearitySolveTask

classLinearitySolveTask(*, config=None, log=None, initInputs=None, **kwargs): Fit the linearity from the PTC dataset...

attributeconfig: Access configuration fields and retargetable subtasks.

methodrun(inputPtc, dummy, camera, inputDims, inputPhotodiodeCorrection=None): Fit non-linearity to PTC data, returning the correct Linearizer object...

Retargetable subtasks¶

No subtasks.

Configuration fields¶

applyPhotodiodeCorrection¶

Default: False
Field type: bool Field

Calculate and apply a correction to the photodiode readings?

connections¶

Data type: lsst.pipe.base.config.LinearitySolveConfigConnections
Field type: ConfigField

Configurations describing the connections of the PipelineTask to datatypes

ignorePtcMask¶

Default: False
Field type: bool Field

Ignore the expIdMask set by the PTC solver?

linearityType¶

Default

'Squared'

Field type

str ChoiceField (optional)

Choices

'LookupTable': Create a lookup table solution.
'Polynomial': Create an arbitrary polynomial solution.
'Squared': Create a single order squared solution.
'Spline': Create a spline based solution.
'None': Create a dummy solution.
None: Field is optional

Type of linearizer to construct.

maxLinearAdu¶

Default: 20000.0
Field type: float Field

Maximum DN value to use to estimate linear term.

maxLookupTableAdu¶

Default: 262144
Field type: int Field

Maximum DN value for a LookupTable linearizer.

minLinearAdu¶

Default: 30.0
Field type: float Field

Minimum DN value to use to estimate linear term.

nSigmaClipLinear¶

Default: 5.0
Field type: float Field

Maximum deviation from linear solution for Poissonian noise.

polynomialOrder¶

Default: 3
Field type: int RangeField
Range: [2,inf)

Degree of polynomial to fit. Must be at least 2.

saveLogOutput¶

Default: True
Field type: bool Field

Flag to enable/disable saving of log output for a task, enabled by default.

splineFitMaxIter¶

Default: 20
Field type: int Field

Maximum number of iterations for spline fit.

splineFitMaxRejectionPerIteration¶

Default: 5
Field type: int Field

Maximum number of rejections per iteration for spline fit.

splineFitMinIter¶

Default: 3
Field type: int Field

Minimum number of iterations for spline fit.

splineGroupingColumn¶

Default: None
Field type: str Field (optional)

Column to use for grouping together points for Spline mode, to allow for different proportionality constants. If not set, no grouping will be done.

splineGroupingMinPoints¶

Default: 100
Field type: int Field

Minimum number of linearity points to allow grouping together points for Spline mode with splineGroupingColumn. This configuration is here to prevent misuse of the Spline code to avoid over-fitting.

splineKnots¶

Default: 10
Field type: int Field

Number of spline knots to use in fit.

usePhotodiode¶

Default: False
Field type: bool Field

Use the photodiode info instead of the raw expTimes?

Debugging¶

linearFit: Display the linearity solution after the initial linear fit (bool)?
polyFit: Display the linearity solution after generating the polynomial fit (bool)?
splineFit: Display the linearity solution after generating the spline fit (bool)?
solution: Display the final linearity solution (bool)?

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