lar::util Namespace Reference

LArSoft utility namespace. More...

Namespaces
	detail
	details
	LArSoft utility implementation details.
	simple_geo
	Simple class definitions for geometry concepts.

Classes
struct	RealComparisons
	Provides simple real number checks. More...
struct	Vector2DComparison
	Class comparing 2D vectors. More...
struct	Vector3DComparison
	Class comparing 2D vectors. More...
struct	assns_has_metadata
	Trait: value true if Assns (association or its node) has metadata. More...
struct	assns_metadata_type
	Trait: type is metadata in Assns (association or its node). More...
struct	assns_iterator_type
	Trait: type is iterator of Assns. More...
struct	assns_traits
	Data types for the specified association type (or its node). More...
struct	assns_metadata_type< art::Assns< L, R, D > >
struct	assns_metadata_type< art::AssnsNode< L, R, D > >
struct	assns_metadata_type< std::pair< art::Ptr< L >, art::Ptr< R > > >
struct	assns_iterator_type< art::Assns< L, R, D > >
struct	assns_iterator_type< art::Assns< L, R, void > >
struct	assns_traits< art::Assns< L, R, D > >
struct	assns_traits< art::AssnsNode< L, R, D > >
struct	assns_traits< std::pair< art::Ptr< L >, art::Ptr< R > > >
struct	assns_metadata_type< proxy::details::AssnsNode< ArtAssnsIterValue > >
class	ChiSquareAccumulator
	Computes a χ from expectation function and data points. More...
struct	dereferenced_type
	Class defining the dereferenced type of the specified type. More...
class	LinearFit
	Performs a linear regression of data. More...
class	QuadraticFit
	Performs a second-degree fit of data. More...
class	GaussianFit
	"Fast" Gaussian fit More...
struct	identity
	A unary functor returning its own argument (any type) More...
class	StatCollector
	Collects statistics on a single quantity (weighted) More...
class	StatCollector2D
	Collects statistics on two homogeneous quantities (weighted) More...
class	MinMaxCollector
	Keeps track of the minimum and maximum value we observed. More...

Typedefs
template<typename Iter >
using	DereferenceConstIterator = detail::DereferenceIteratorBase< Iter, std::add_const_t< std::decay_t< decltype(**(std::declval< Iter >()))>> >
	An iterator wrapper to dereference pointed values. More...
template<typename Iter >
using	DereferenceIterator = detail::DereferenceIteratorBase< Iter, std::decay_t< decltype(**(std::declval< Iter >()))> >
	An iterator wrapper to dereferencing pointed values as constant. More...
using	HitToWire = details::FindAllP< recob::Hit, recob::Wire >
	Query object connecting a hit to a wire. More...
template<typename Assns >
using	assns_metadata_t = typename assns_metadata_type< Assns >::type
	Trait: type of metadata in Assns (association or its node). More...
template<typename Assns >
using	assns_iterator_t = typename assns_iterator_type< Assns >::type
	Trait: type of iterator of Assns. More...

Functions
template<typename Iter >
auto	makeDereferenceIterator (Iter &&iter)
	Returns a dereference iterator to the begin of specified container. More...
template<typename Cont >
auto	beginDereferenceIterator (Cont &cont)
	Returns a dereference iterator to the begin of specified container. More...
template<typename Cont >
auto	endDereferenceIterator (Cont &cont)
	Returns a dereference iterator to the end of specified container. More...
template<typename Cont >
auto	rbeginDereferenceIterator (Cont &cont)
	Returns a dereference reverse iterator to the begin of container. More...
template<typename Cont >
auto	rendDereferenceIterator (Cont &cont)
	Returns a dereference reverse iterator to the end of container. More...
template<typename Cont >
auto	dereferenceIteratorLoop (Cont &cont)
	Returns an object enabling a dereferencing range-for loop. More...
template<typename Cont >
auto	dereferenceIteratorReverseLoop (Cont &cont)
	Returns an object enabling a dereferencing reverse range-for loop. More...
template<typename RealType >
auto	makeVector2DComparison (RealType threshold)
	Creates a Vector2DComparison from a RealComparisons object. More...
template<typename RealType >
auto	makeVector2DComparison (lar::util::RealComparisons< RealType > const &comp)
	Creates a Vector2DComparison from a RealComparisons object. More...
template<typename RealType >
auto	makeVector3DComparison (RealType threshold)
	Creates a Vector3DComparison from a RealComparisons object. More...
template<typename RealType >
auto	makeVector3DComparison (lar::util::RealComparisons< RealType > const &comp)
	Creates a Vector3DComparison from a RealComparisons object. More...
double	TrackProjectedLength (recob::Track const &track, geo::View_t view)
	Returns the length of the projection of a track on a view. More...
double	TrackPitchInView (recob::Track const &track, geo::View_t view, size_t trajectory_point=0U)
	Returns the projected length of track on a wire pitch step [cm]. More...
template<typename F >
auto	makeChiSquareAccumulator (F &&e)
	Creates a ChiSquareAccumulator object with the specified function. More...
template<typename T , typename F >
auto	makeChiSquareAccumulator (F &&e)
	Creates a ChiSquareAccumulator object with the specified function. More...
template<typename T >
details::dereference_class< T, details::has_dereference_class < T >::value >::reference_type	dereference (T &v)
	Returns the value pointed by the argument, or the argument itself. More...
template<typename T >
details::make_pointer_class< T, details::has_dereference_class < T >::value >::pointer_type	make_pointer (T &v)
	Returns a pointer to the value of argument, or the argument itself. More...
Constant iterator functions
See the documentation of the similar non-const ones.
template<typename Iter >
auto	makeDereferenceConstIterator (Iter &&iter)
template<typename Cont >
auto	cbeginDereferenceIterator (Cont &cont)
template<typename Cont >
auto	cendDereferenceIterator (Cont &cont)
template<typename Cont >
auto	crbeginDereferenceIterator (Cont &cont)
template<typename Cont >
auto	crendDereferenceIterator (Cont &cont)
template<typename Cont >
auto	dereferenceConstIteratorLoop (Cont &cont)
	Returns an object enabling a dereferencing range-for loop. More...
template<typename Cont >
auto	dereferenceConstIteratorReverseLoop (Cont &cont)
	Returns an object enabling a dereferencing reverse range-for loop. More...

Variables
template<typename Assns >
constexpr bool	assns_has_metadata_v = assns_has_metadata<Assns>::value
	Trait: true if Assns (association or its node) has metadata. More...

Detailed Description

LArSoft utility namespace.

LArSoft utilities namespace.

Typedef Documentation

template<typename Iter >

using lar::util::DereferenceConstIterator = typedef detail::DereferenceIteratorBase< Iter, std::add_const_t<std::decay_t<decltype(**(std::declval<Iter>()))>> >

An iterator wrapper to dereference pointed values.

---

Template Parameters

Iter	type of iterator being wrapped

See Also

beginDereferenceIterator(), endDereferenceIterator(), dereferenceIteratorLoop()

This iterator is useful to iterate a collection of pointers accessing directly the pointed values.

It's probably easier to use cbeginDereferenceIterator(), cendDereferenceIterator() and dereferenceConstIteratorLoop() rather than instantiating this class directly.

Note

Note the bizarre construction mechanism, needed to differentiate from copy constructor. This allows nesting iterators.

Deprecated:

Just use boost::indirect_iterator instead (boost/iterator/indirect_iterator.hpp).

Definition at line 220 of file DereferenceIterator.h.

template<typename Iter >

using lar::util::DereferenceIterator = typedef detail::DereferenceIteratorBase< Iter, std::decay_t<decltype(**(std::declval<Iter>()))> >

An iterator wrapper to dereferencing pointed values as constant.

Template Parameters

Iter	type of iterator being wrapped

See Also

DereferenceConstIterator

This class behaves like DereferenceConstIterator, except that it returns mutable references to values.

Deprecated:

Just use boost::indirect_iterator instead (boost/iterator/indirect_iterator.hpp).

Definition at line 237 of file DereferenceIterator.h.

using lar::util::HitToWire = typedef details::FindAllP<recob::Hit, recob::Wire>

Query object connecting a hit to a wire.

---

Once upon a time, recob::Hit had a art::Ptr<recob::Wire> in it, and life was easy. When it was discovered that art pointers in data products were evil, they were banned from recob::Hit. As always, evil turns out to be convenient. This query object tries to provide in an efficient way a connection between a hit and the wire that has generated it.

This object expects

Example of usage: let hit_ptr be a valid art::Ptr<recob::Hit>. Then

HitToWire HtoW(evt);
art::Ptr<recob::Wire> wire_ptr = HtoW[hit_ptr];

If the association label is known, it can be used to selectively load that association:

HitToWire HtoW(evt, AssociationInputTag);
art::Ptr<recob::Wire> wire_ptr = HtoW[hit_ptr];

that has little advantage (in fact, it is possibly slower) respect to using art::FindOneP.

Definition at line 56 of file HitUtils.h.

Function Documentation

template<typename Cont >

auto lar::util::beginDereferenceIterator

(

Cont &

cont

)

Returns a dereference iterator to the begin of specified container.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

a dereference iterator of cont.begin()

If the type is constant, the iterator will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 269 of file DereferenceIterator.h.

      { return makeDereferenceIterator(cont.begin()); }

template<typename Cont >

auto lar::util::cbeginDereferenceIterator

(

Cont &

cont

)

See Also

beginDereferenceIterator

Definition at line 395 of file DereferenceIterator.h.

      { return makeDereferenceConstIterator(cont.cbegin()); }

template<typename Cont >

auto lar::util::cendDereferenceIterator

(

Cont &

cont

)

See Also

endDereferenceIterator

Definition at line 400 of file DereferenceIterator.h.

      { return makeDereferenceConstIterator(cont.cend()); }

template<typename Cont >

auto lar::util::crbeginDereferenceIterator

(

Cont &

cont

)

See Also

rbeginDereferenceIterator

Definition at line 405 of file DereferenceIterator.h.

      { return makeDereferenceConstIterator(cont.crbegin()); }

template<typename Cont >

auto lar::util::crendDereferenceIterator

(

Cont &

cont

)

See Also

crendDereferenceIterator

Definition at line 410 of file DereferenceIterator.h.

      { return makeDereferenceConstIterator(cont.crend()); }

template<typename T >

details::dereference_class<T, details::has_dereference_class<T>::value>::reference_type lar::util::dereference ( T &  v )

inline

Returns the value pointed by the argument, or the argument itself.

---

Template Parameters

T	the type of the argument

Parameters

v	the value to be dereferenced

Returns

the value v points to, if any, or v itself

This function allows the use of the same template code to process both pointers and pointed values. For example:

template <typename T>
std::vector<int> extract_int(std::vector<T> const& from) {
  std::vector<int> v;
  v.reserve(from.size());
  std::transform(from.begin(), from.end(), std::back_inserter(v),
    util::dereference);
  return v;
}

int value = 10;
std::vector<int> v(10, value);
std::vector<int*> v_ptr(10, &value);

extract_int(v);
extract_int(v_ptr);

shows that the same function can be used on vectors of integers and of their pointers.

Definition at line 254 of file Dereference.h.

      {
        return details::dereference_class
          <T, details::has_dereference_class<T>::value>()(v);
      }

template<typename Cont >

auto lar::util::dereferenceConstIteratorLoop

(

Cont &

cont

)

Returns an object enabling a dereferencing range-for loop.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

an object enabling a dereferencing range-for loop

See Also

dereferenceIteratorReverseLoop()

Example of usage:

std::vector<std::unique_ptr<int>> v;

// fill the vector

for (int const& i: dereferenceConstIteratorLoop(v)) {

  std::cout << i << std::endl;

} // for i

This wrapper forces the iteration variable to be constant.

Definition at line 436 of file DereferenceIterator.h.

      {
        return detail::makeIteratorBox
          (cbeginDereferenceIterator(cont), cendDereferenceIterator(cont));
      } // dereferenceConstIteratorLoop()

template<typename Cont >

auto lar::util::dereferenceConstIteratorReverseLoop

(

Cont &

cont

)

Returns an object enabling a dereferencing reverse range-for loop.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

an object enabling a dereferencing range-for loop

See Also

dereferenceConstIteratorLoop()

This function is similar to dereferenceConstIteratorLoop(), but the order of iteration is reversed.

Example of usage:

std::vector<std::unique_ptr<int>> v;

// fill the vector

for (int const& i: dereferenceConstIteratorReverseLoop(v)) {

  std::cout << i << std::endl;

} // for i

If the type is constant, the loop variable will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 472 of file DereferenceIterator.h.

      {
        return detail::makeIteratorBox
          (crbeginDereferenceIterator(cont), crendDereferenceIterator(cont));
      } // dereferenceConstIteratorReverseLoop()

template<typename Cont >

auto lar::util::dereferenceIteratorLoop

(

Cont &

cont

)

Returns an object enabling a dereferencing range-for loop.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

an object enabling a dereferencing range-for loop

See Also

dereferenceIteratorReverseLoop()

Example of usage:

std::vector<std::unique_ptr<int>> v;

// fill the vector

for (int& i: dereferenceIteratorLoop(v)) {

  std::cout << i << std::endl;

} // for i

If the type is constant, the loop variable will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 340 of file DereferenceIterator.h.

      {
        return detail::makeIteratorBox
          (beginDereferenceIterator(cont), endDereferenceIterator(cont));
      } // dereferenceIteratorLoop()

template<typename Cont >

auto lar::util::dereferenceIteratorReverseLoop

(

Cont &

cont

)

Returns an object enabling a dereferencing reverse range-for loop.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

an object enabling a dereferencing range-for loop

See Also

dereferenceIteratorLoop()

This function is similar to dereferenceIteratorLoop(), but the order of iteration is reversed.

Example of usage:

std::vector<std::unique_ptr<int>> v;

// fill the vector

for (int& i: dereferenceIteratorReverseLoop(v)) {

  std::cout << i << std::endl;

} // for i

If the type is constant, the loop variable will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 376 of file DereferenceIterator.h.

      {
        return detail::makeIteratorBox
          (rbeginDereferenceIterator(cont), rendDereferenceIterator(cont));
      } // dereferenceIteratorReverseLoop()

template<typename Cont >

auto lar::util::endDereferenceIterator

(

Cont &

cont

)

Returns a dereference iterator to the end of specified container.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

a dereference iterator of cont.end()

If the type is constant, the iterator will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 283 of file DereferenceIterator.h.

      { return makeDereferenceIterator(cont.end()); }

template<typename T >

details::make_pointer_class<T, details::has_dereference_class<T>::value>::pointer_type lar::util::make_pointer ( T &  v )

inline

Returns a pointer to the value of argument, or the argument itself.

---

Template Parameters

T	the type of the argument

Parameters

v	the value to be taken the pointer of

Returns

a pointer to v, or v itself if it is already a C pointer

This function allows the use of the same template code to process both pointers and pointed values. For example:

template <typename T>
std::vector<int*> extract_int(std::vector<T> const& from) {
  std::vector<int*> v;
  v.reserve(from.size());
  std::transform(from.begin(), from.end(), std::back_inserter(v),
    util::make_pointer);
  return v;
}

int value = 10;
std::vector<int> v(10, value);
std::vector<int*> v_ptr(10, &value);

extract_int(v);
extract_int(v_ptr);

shows that the same function can be used on vectors of integers and of their pointers.

Definition at line 293 of file Dereference.h.

      {
        return details::make_pointer_class
          <T, details::has_dereference_class<T>::value>()(v);
      }

template<typename F >

auto lar::util::makeChiSquareAccumulator

(

F &&

e

)

Creates a ChiSquareAccumulator object with the specified function.

Template Parameters

F	type of function (deduced from e)

Parameters

e	expectation function

Returns

a ChiSquareAccumulator<F> instance with specified expectation

Example of usage:

auto zero = [](double){ return 0.0; }; // expectation function
auto chiSquare = lar::util::makeChiSquareAccumulator(zero);

declare chiSquare in a way equivalent to: lar::util::ChiSquareAccumulator<decltype(zero)> chiSquare(zero).

Definition at line 161 of file ChiSquareAccumulator.h.

      { return lar::util::ChiSquareAccumulator<F>(std::forward<F>(e)); }

template<typename T , typename F >

auto lar::util::makeChiSquareAccumulator

(

F &&

e

)

Creates a ChiSquareAccumulator object with the specified function.

Template Parameters

T	type of data (default: double)
F	type of function (deduced from e)

Parameters

e	expectation function

Returns

a ChiSquareAccumulator<F,T> instance with specified expectation

Example of usage:

auto zero = [](float){ return 0.0F; }; // expectation function
auto chiSquare = lar::util::makeChiSquareAccumulator<float>(zero);

declare chiSquare in a way equivalent to: lar::util::ChiSquareAccumulator<decltype(zero), float> chiSquare(zero).

Definition at line 180 of file ChiSquareAccumulator.h.

      { return lar::util::ChiSquareAccumulator<F, T>(std::forward<F>(e)); }

template<typename Iter >

auto lar::util::makeDereferenceConstIterator

(

Iter &&

iter

)

See Also

makeDereferenceIterator

Definition at line 390 of file DereferenceIterator.h.

      { return DereferenceConstIterator<Iter>(std::forward<Iter>(iter), {}); }

template<typename Iter >

auto lar::util::makeDereferenceIterator

(

Iter &&

iter

)

Returns a dereference iterator to the begin of specified container.

Template Parameters

Iter	type of the iterator to be wrapped (may be constant)

Parameters

iter	the iterator to be wrapped

Returns

a dereference iterator of iter

See Also

beginDereferenceIterator(), endDereferenceIterator(), rbeginDereferenceIterator(), rendDereferenceIterator(), dereferenceIteratorLoop(), dereferenceIteratorReverseLoop()

If the type is constant, the iterator will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 255 of file DereferenceIterator.h.

      { return DereferenceIterator<Iter>(std::forward<Iter>(iter), {}); }

template<typename RealType >

auto lar::util::makeVector2DComparison

(

RealType

threshold

)

Creates a Vector2DComparison from a RealComparisons object.

Definition at line 187 of file RealComparisons.h.

      { return Vector2DComparison<RealType>(threshold); }

template<typename RealType >

auto lar::util::makeVector2DComparison

(

lar::util::RealComparisons< RealType > const &

comp

)

Creates a Vector2DComparison from a RealComparisons object.

Definition at line 193 of file RealComparisons.h.

      { return Vector2DComparison<RealType>(comp); }

template<typename RealType >

auto lar::util::makeVector3DComparison

(

RealType

threshold

)

Creates a Vector3DComparison from a RealComparisons object.

Definition at line 252 of file RealComparisons.h.

      { return Vector3DComparison<RealType>(threshold); }

template<typename RealType >

auto lar::util::makeVector3DComparison

(

lar::util::RealComparisons< RealType > const &

comp

)

Creates a Vector3DComparison from a RealComparisons object.

Definition at line 258 of file RealComparisons.h.

      { return Vector3DComparison<RealType>(comp); }

template<typename Cont >

auto lar::util::rbeginDereferenceIterator

(

Cont &

cont

)

Returns a dereference reverse iterator to the begin of container.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

a dereference iterator of cont.rbegin()

If the type is constant, the iterator will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 297 of file DereferenceIterator.h.

      { return makeDereferenceIterator(cont.rbegin()); }

template<typename Cont >

auto lar::util::rendDereferenceIterator

(

Cont &

cont

)

Returns a dereference reverse iterator to the end of container.

Template Parameters

Cont	type of the container (may be constant)

Parameters

cont	container to extract the iterator from

Returns

a dereference iterator of cont.rend()

If the type is constant, the iterator will likely be constant too. This wrapper is quite blind to the meaning of iterators and their constantness.

Definition at line 311 of file DereferenceIterator.h.

      { return makeDereferenceIterator(cont.rend()); }

double lar::util::TrackPitchInView	(	recob::Track const &	track,
		geo::View_t	view,
		size_t	trajectory_point = 0U
	)

Returns the projected length of track on a wire pitch step [cm].

Parameters

track	the track to be projected on a view
view	the view for track projection
trajectory_point	at which point of the track to look for the pitch (default: 0)

Returns

wire pitch along the track direction at its specified point [cm]

Exceptions

cet::exception	(category "TrackPitchInView") if the trajectory_point index is not valid in track
cet::exception	(category "Geometry") if the point is in no TPC
cet::exception	(category "TPCGeo") if the view is unknown, not available or otherwise invalid
cet::exception	(category "Track") if the track projection on the wire plane is parallel to the wires (< 0.01%)

This function returns the distance covered by the track between two wires, projected on the wire plane. The direction of the track is the one at the specified trajectory point (the first one by default). That direction is projected on the wire plane with the specified view within the TPC that contains that point.

The returned value is the distance, in centimeters, between two consecutive wires on that projected direction. This is always a positive number, regardless the direction of the track, and never smaller than the wire pitch on the projection wire plane.

Definition at line 79 of file TrackUtils.cxx.

{
   /*
    * The plan:
    * 1. find the wire plane we are talking about
    *    (in the right TPC and with the right view)
    * 2. ask the plane the answer
    *
    */


   if(trajectory_point >= track.NumberTrajectoryPoints()) {
      cet::exception("TrackPitchInView") << "ERROR: Asking for trajectory point #"
         << trajectory_point << " when trajectory vector size is of size "
         << track.NumberTrajectoryPoints() << ".\n";
   }
   recob::Track::TrajectoryPoint_t const& point
     = track.TrajectoryPoint(trajectory_point);

   // this throws if the position is not in any TPC,
   // or if there is no view with specified plane
   auto const& geom = *(lar::providerFrom<geo::Geometry>());
   geo::PlaneGeo const& plane = geom.PositionToTPC(point.position).Plane(view);

#if 0 // this can be enabled after `geo::PlaneGeo::InterWireProjectedDistance()` becomes available in larcorealg
   double const d = plane.InterWireProjectedDistance(point.direction());

   // do we prefer to just return the value and let the caller check it?
   if (d > 50.0 * plane.WirePitch()) { // after many pitches track would scatter
      throw cet::exception("Track")
        << "track at point #" << trajectory_point
        << " is almost parallel to the wires in view "
        << geo::PlaneGeo::ViewName(view) << " (wire direction is "
        << plane.GetWireDirection<geo::Vector_t>() << "; track direction is "
        << point.direction()
        << ").\n";
   }
   return d;

#else // !0
   //
   // 2. project the direction of the track on that plane
   //
   // this is the projection of the direction of the track on the wire plane;
   // it is 2D and its second component ("Y()") is on wire coordinate direction;
   // remember that the projection modulus is smaller than 1 because it is
   // the 3D direction versor, deprived of its drift direction component
   auto const& proj = plane.Projection(point.direction());

   if (lar::util::RealComparisons(1e-4).zero(proj.Y())) {
      throw cet::exception("Track")
        << "track at point #" << trajectory_point
        << " is almost parallel to the wires in view "
        << geo::PlaneGeo::ViewName(view) << " (wire direction is "
        << plane.GetWireDirection<geo::Vector_t>() << "; track direction is "
        << point.direction()
        << ", its projection on plane " << plane.ID() << " is " << proj
        << ").\n";
   }

   //
   // 3. scale that projection so that it covers a wire pitch worth in the wire
   //    coordinate direction;
   //    WirePitch() is what gives this vector a physical size [cm]
   //
   return proj.R() / std::abs(proj.Y()) * plane.WirePitch();
#endif // ?0

} // lar::util::TrackPitchInView()

double lar::util::TrackProjectedLength	(	recob::Track const &	track,
		geo::View_t	view
	)

Returns the length of the projection of a track on a view.

Parameters

track	the track to be projected on a view
view	the view to project the track on

Returns

length of the projection, in centimetres

Todo:

CAREFUL: using view to determine projected length does not work for DUNE. Need to think more about this.

Todo:

is this right, or should it be dist*cosgamma???

Definition at line 35 of file TrackUtils.cxx.

                                                                            {

   if(view == geo::kUnknown) {
      throw cet::exception("TrackProjectedLength") << "cannot provide projected length for "
        << "unknown view\n";
   }
   double length = 0.;

   auto const* geom = lar::providerFrom<geo::Geometry>();
   double angleToVert = 0.;
   for(unsigned int i = 0; i < geom->Nplanes(); ++i){
      if(geom->Plane(i).View() == view){
         angleToVert = geom->Plane(i).Wire(0).ThetaZ(false) - 0.5*::util::pi<>();
         break;
      }
   }

   // now loop over all points in the trajectory and add the contribution to the
   // to the desired view

   for(size_t p = 1; p < track.NumberTrajectoryPoints(); ++p){
      const auto& pos_cur = track.LocationAtPoint(p);
      const auto& pos_prev = track.LocationAtPoint(p - 1);
      double dist = std::sqrt( std::pow(pos_cur.x() - pos_prev.x(), 2) +
         std::pow(pos_cur.y() - pos_prev.y(), 2) +
         std::pow(pos_cur.z() - pos_prev.z(), 2) );

      // (sin(angleToVert),cos(angleToVert)) is the direction perpendicular to wire
      // fDir[p-1] is the direction between the two relevant points
      const auto& dir_prev = track.DirectionAtPoint(p - 1);
      double cosgamma = std::abs(std::sin(angleToVert)*dir_prev.Y() +
         std::cos(angleToVert)*dir_prev.Z() );

      /// @todo is this right, or should it be dist*cosgamma???
      length += dist/cosgamma;
   } // end loop over distances between trajectory points

   return length;
} // lar::util::TrackProjectedLength()