CalcMomentSize

class lsst.analysis.tools.actions.vector.CalcMomentSize(*args, **kw)

Bases: VectorAction

Calculate a size based on 2D moments.

Given a 2x2 matrix of moments (i.e. moment of inertia), two sizes can be defined as follows:

Determinant radius: \((I_{xx}I_{yy}-I_{xy}^2)^{\frac{1}{4}}\) Trace radius: \(\sqrt{(I_{xx}+I_{yy})/2}\)

The square of size measure is typically expressed either as the arithmetic mean of the eigenvalues of the moment matrix (trace radius) or as the geometric mean of the eigenvalues (determinant radius), which can be specified using the sizeType parameter. Both of these measures correspond to the \(\sigma^2\) parameter for a 2D Gaussian.

Notes

Since lensing preserves surface brightness, the determinant radius relates the magnification cleanly as it is derived from the area of isophotes, but have a slightly higher chance of being NaNs for noisy moment estimates.

Attributes Summary

colXx	The column name to get the xx shape component from.
colXy	The column name to get the xy shape component from.
colYy	The column name to get the yy shape component from.
is_covariance	Whether the fields are for a covariance matrix.
sizeType	The type of size to calculate (str, default 'determinant')

Methods Summary

__call__(data, **kwargs)	Call self as a function.
getInputSchema()	Return the schema an AnalysisAction expects to be present in the arguments supplied to the __call__ method.
validate()	Validate the Config, raising an exception if invalid.

Attributes Documentation

colXx

The column name to get the xx shape component from. (str, default '{band}_ixx')

colXy

The column name to get the xy shape component from. (str, default '{band}_ixy')

colYy

The column name to get the yy shape component from. (str, default '{band}_iyy')

is_covariance

Whether the fields are for a covariance matrix. If False, the XX/YY/XY terms are instead assumed to map to sigma_x/sigma_y/rho. (bool, default True)

sizeType

The type of size to calculate (str, default 'determinant')

Allowed values:

'trace'

Trace radius \(\sqrt{(I_{xx}+I_{yy})/2}\)

'determinant'

Determinant radius \((I_{xx}I_{yy}-I_{xy}^2)^{\frac{1}{4}}\)

Methods Documentation

__call__(data: MutableMapping[str, ndarray[Any, dtype[ScalarType]] | Scalar | HealSparseMap | Tensor], **kwargs) → ndarray[Any, dtype[ScalarType]]

Call self as a function.

getInputSchema() → Tensor]]]

Return the schema an AnalysisAction expects to be present in the arguments supplied to the __call__ method.

Returns:

resultKeyedDataSchema

The schema this action requires to be present when calling this action, keys are unformatted.

validate()

Validate the Config, raising an exception if invalid.

Raises:

lsst.pex.config.FieldValidationError

Raised if verification fails.

Notes

The base class implementation performs type checks on all fields by calling their validate methods.

Complex single-field validation can be defined by deriving new Field types. For convenience, some derived lsst.pex.config.Field-types (ConfigField and ConfigChoiceField) are defined in lsst.pex.config that handle recursing into subconfigs.

Inter-field relationships should only be checked in derived Config classes after calling this method, and base validation is complete.