SingleFrameMomentsClassifierPlugin

class lsst.meas.base.SingleFrameMomentsClassifierPlugin(config, name, schema, metadata)

Bases: SingleFramePlugin

Classify objects by comparing their moments-based trace radius to PSF’s.

The plugin computes chi^2 as ((T_obj - T_psf)/T_psf^exponent)^2, where T_obj is the sum of Ixx and Iyy moments of the object, and T_psf is the sum of Ixx and Iyy moments of the PSF. The exponent is configurable. The measure of being a galaxy is then 1 - exp(-0.5*chi^2).

Parameters:

configMomentsClassifierConfig

Plugin configuration.

namestr

Plugin name.

schemaSchema

The schema for the measurement output catalog. New fields will be added to hold measurements produced by this plugin.

metadataPropertySet

Plugin metadata that will be attached to the output catalog.

Notes

The measure method of the plugin requires a value for the exposure argument to maintain consistent API, but it is not used in the measurement.

Attributes Summary

APCORR_ORDER	Order for algorithms which require shape, centroid and flux (float).
CENTROID_ORDER	Order for algorithms which require only Footprint and Peaks (float).
DEFAULT_CATALOGCALCULATION	Order for catalog calculation plugins.
FAILURE_BAD_SHAPE	Denotes failures due to bad shape (int).
FLUX_ORDER	Order for algorithms which require a shape and a centroid (float).
SHAPE_ORDER	Order for algorithms which require a centroid (float).
registry	Registry of subclasses of SingleFramePlugin (PluginRegistry).

Methods Summary

fail(measRecord[, error])	Record a failure of the measure or measureN method.
getExecutionOrder()	Get the relative execution order of this plugin.
getLogName()
getTransformClass()	Get the measurement transformation appropriate to this plugin.
measure(measRecord, exposure)	Measure the properties of a source on a single image.
measureN(measCat, exposure)	Measure the properties of blended sources on a single image.

Attributes Documentation

APCORR_ORDER = 3.0

Order for algorithms which require shape, centroid and flux (float).

Notes

These algorithms may assume that getCentroid and getShape will return good values, that flux has been measured, and that and that a Footprint and its Peaks are available.

CENTROID_ORDER = 0.0

Order for algorithms which require only Footprint and Peaks (float).

Notes

Algorithms with this execution order include centroids.

DEFAULT_CATALOGCALCULATION = 4.0

Order for catalog calculation plugins.

Notes

These plugins only operate on catalogs; they may not access pixel values.

FAILURE_BAD_SHAPE = 1

Denotes failures due to bad shape (int).

FLUX_ORDER = 2.0

Order for algorithms which require a shape and a centroid (float).

Notes

These algorithms may assume that both getCentroid and getShape will return good values, and that a Footprint and its Peaks are available.

SHAPE_ORDER = 1.0

Order for algorithms which require a centroid (float).

Notes

These algorithms may refer assume that getCentroid will return a good centroid, and that a Footprint and its Peaks are available.

registry = <lsst.meas.base.pluginRegistry.PluginRegistry object>

Registry of subclasses of SingleFramePlugin (PluginRegistry).

Methods Documentation

fail(measRecord, error=None) → None

Record a failure of the measure or measureN method.

Parameters:

measRecordlsst.afw.table.SourceRecord

Table record describing the source being measured.

errorMeasurementError, optional

Only provided if the measurement failed due to a MeasurementError being raised; otherwise, will be None.

Notes

When the plugin raises an exception, framework will call BasePlugin.fail to allow the plugin to set its failure flag field(s). When BasePlugin.measureN raises an exception, BasePlugin.fail will be called repeatedly with all the records that were being measured.

If the exception is an MeasurementError, it will be passed as the error argument; in all other cases the error argument will be None, and the failure will be logged by the measurement framework as a warning.

classmethod getExecutionOrder()

Get the relative execution order of this plugin.

Must be reimplemented as a class method by concrete derived classes.

getLogName()

static getTransformClass()

Get the measurement transformation appropriate to this plugin.

This returns a subclass of transforms.MeasurementTransform, which may be instantiated with details of the algorithm configuration and then called with information about calibration and WCS to convert from raw measurement quantities to calibrated units. Calibrated data is then provided in a separate output table.

Notes

By default, we copy everything from the input to the output without transformation.

measure(measRecord, exposure) → None

Measure the properties of a source on a single image.

The image may be from a single epoch, or it may be a coadd.

Parameters:

measRecordlsst.afw.table.SourceRecord

Record describing the object being measured. Previously-measured quantities may be retrieved from here, and it will be updated in-place tih the outputs of this plugin.

exposurelsst.afw.image.ExposureF

The pixel data to be measured, together with the associated PSF, WCS, etc. All other sources in the image should have been replaced by noise according to deblender outputs.

measureN(measCat, exposure)

Measure the properties of blended sources on a single image.

This operates on all members of a blend family at once. The image may be from a single epoch, or it may be a coadd.

Parameters:

measCatlsst.afw.table.SourceCatalog

Catalog describing the objects (and only those objects) being measured. Previously-measured quantities will be retrieved from here, and it will be updated in-place with the outputs of this plugin.

exposurelsst.afw.image.ExposureF

The pixel data to be measured, together with the associated PSF, WCS, etc. All other sources in the image should have been replaced by noise according to deblender outputs.

Notes

Derived classes that do not implement measureN should just inherit this disabled version. Derived classes that do implement measureN should additionally add a bool doMeasureN config field to their config class to signal that measureN-mode is available.