Class Acts::Measurement¶
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template<typename indices_t, size_t kSize>
class Acts::Measurement¶ A measurement of a fixed-size subspace of the full parameters.
The measurement intentionally does not store a pointer/reference to the reference object in the geometry hierarchy, i.e. the surface or volume. The reference object can already be identified via the geometry identifier provided by the source link. Since a measurement must be anchored within the geometry hierarchy, all measurement surfaces and volumes must provide valid geometry identifiers. In all use-cases, e.g. Kalman filtering, a pointer/reference to the reference object is available before the measurement is accessed; e.g. the propagator provides the surface pointer during navigation, which is then used to lookup possible measurements.
- tparam indices_t
Parameter index type, determines the full parameter space
- tparam kSize
Size of the parameter subset.
The pointed-to geometry object would differ depending on the parameter type. This means either, that there needs to be an additional variable type or that a pointer to a base object is stored (requiring a
dynamic_cast
later on). Both variants add additional complications. Since the geometry object is not required anyways (as discussed above), not storing it removes all these complications altogether.Public Types
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using CovarianceMatrix = ActsSymMatrix<kSize>¶
Matrix type for the measurement covariance.
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using ExpansionMatrix = ActsMatrix<kFullSize, kSize>¶
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using FullParametersVector = ActsVector<kFullSize>¶
Vector type containing all parameters in the same space.
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using ParametersVector = ActsVector<kSize>¶
Vector type containing for measured parameter values.
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using ProjectionMatrix = ActsMatrix<kSize, kFullSize>¶
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using Scalar = ActsScalar¶
Public Functions
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template<typename parameters_t, typename covariance_t>
inline Measurement(const SourceLink &source, const std::array<indices_t, kSize> &indices, const Eigen::MatrixBase<parameters_t> ¶ms, const Eigen::MatrixBase<covariance_t> &cov)¶ Construct from source link, subset indices, and measured data.
Note
The indices must be ordered and must describe/match the content of parameters and covariance.
- Template Parameters
parameters_t – Input parameters vector type
covariance_t – Input covariance matrix type
- Parameters
source – The link that connects to the underlying detector readout
indices – Which parameters are measured
params – Measured parameters values
cov – Measured parameters covariance
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Measurement() = delete¶
A measurement can only be constructed with valid parameters.
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Measurement(const Measurement&) = default¶
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Measurement(Measurement&&) = default¶
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~Measurement() = default¶
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inline const CovarianceMatrix &covariance() const¶
Measured parameters covariance.
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inline ExpansionMatrix expander() const¶
Expansion matrix from the measured subspace into the full space.
This is equivalent to the tranpose of the projection matrix only in the case of a trivial projection matrix. While this is the case here, it is still recommended to use the expansion matrix directly in cases where it is explicitely used.
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inline std::ostream &operator<<(std::ostream &os) const¶
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Measurement &operator=(const Measurement&) = default¶
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Measurement &operator=(Measurement&&) = default¶
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inline const ParametersVector ¶meters() const¶
Measured parameters values.
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inline ProjectionMatrix projector() const¶
Projection matrix from the full space into the measured subspace.
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inline ParametersVector residuals(const FullParametersVector &reference) const¶
Compute residuals in the measured subspace.
This computes the difference
measured - reference
taking into account the allowed parameter ranges. Only the reference values in the measured subspace are used for the computation.- Parameters
reference – Reference parameters in the full space.
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inline const SourceLink &sourceLink() const¶
Source link that connects to the underlying detector readout.
Public Static Functions
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static inline constexpr size_t size()¶
Number of measured parameters.