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* Copyright NumFOCUS

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* Licensed under the Apache License, Version 2.0 (the "License");

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* https://www.apache.org/licenses/LICENSE-2.0.txt

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// Software Guide : BeginLatex

//

// \index{itk::Statistics::EuclideanDistanceMetric}

//

// The Euclidean distance function

// (\subdoxygen{Statistics}{EuclideanDistanceMetric} requires as template

// parameter the type of the measurement vector. We can use this function for

// any subclass of the \doxygen{FixedArray}. As a subclass of the

// \subdoxygen{Statistics}{DistanceMetric}, it has two basic methods, the

// \code{SetOrigin(measurement vector)} and the \code{Evaluate(measurement

// vector)}. The \code{Evaluate()} method returns the distance between its

// argument (a measurement vector) and the measurement vector set by the

// \code{SetOrigin()} method.

//

// In addition to the two methods, EuclideanDistanceMetric has two more

// methods that return the distance of two measurements ---

// \code{Evaluate(measurement vector, measurement vector)} and the

// coordinate distance between two measurements (not vectors) ---

// \code{Evaluate(measurement, measurement)}. The argument type of the

// latter method is the type of the component of the measurement vector.

//

// We include the header files for the class and the \doxygen{Vector}.

//

// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet

#include "itkVector.h"

#include "itkArray.h"

#include "itkEuclideanDistanceMetric.h"

// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex

//

// We define the type of the measurement vector that will be input of

// the Euclidean distance function. As a result, the measurement type

// is \code{float}.

//

// Software Guide : EndLatex

int

main(int, char *[])

{

// Software Guide : BeginCodeSnippet

using MeasurementVectorType = itk::Array<float>;

// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex

//

// The instantiation of the function is done through the usual

// \code{New()} method and a smart pointer.

//

// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet

using DistanceMetricType =

itk::Statistics::EuclideanDistanceMetric<MeasurementVectorType>;

auto distanceMetric = DistanceMetricType::New();

// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex

//

// We create three measurement vectors, the \code{originPoint},

// the \code{queryPointA}, and the \code{queryPointB}. The type of the

// \code{originPoint} is fixed in the

// \subdoxygen{Statistics}{DistanceMetric} base class as

// \code{itk::Vector< double, length of the measurement vector of the

// each distance metric instance>}.

//

// Software Guide : EndLatex

// Software Guide : BeginLatex

//

// The Distance metric does not know about the length of the measurement

// vectors. We must set it explicitly using the

// \code{SetMeasurementVectorSize()} method.

//

// Software Guide : EndLatex

distanceMetric->SetMeasurementVectorSize(2);

// Software Guide : BeginCodeSnippet

DistanceMetricType::OriginType originPoint(2);

MeasurementVectorType queryPointA(2);

MeasurementVectorType queryPointB(2);

originPoint[0] = 0;

originPoint[1] = 0;

queryPointA[0] = 2;

queryPointA[1] = 2;

queryPointB[0] = 3;

queryPointB[1] = 3;

// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex

//

// In the following code snippet, we show the uses of the three different

// \code{Evaluate()} methods.

//

// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet

distanceMetric->SetOrigin(originPoint);

std::cout

<< "Euclidean distance between the origin and the query point A = "

<< distanceMetric->Evaluate(queryPointA) << std::endl;

std::cout << "Euclidean distance between the two query points (A and B) = "

<< distanceMetric->Evaluate(queryPointA, queryPointB)

<< std::endl;

std::cout << "Coordinate distance between "

<< "the first components of the two query points = "

<< distanceMetric->Evaluate(queryPointA[0], queryPointB[0])

<< std::endl;

// Software Guide : EndCodeSnippet

return EXIT_SUCCESS;

}