OxFunctionsT1ThreeParam.hxx
/*!
* \file OxFunctionsT1ThreeParams.hxx
* \author Konrad Werys
* \date 2018/07/29
*/
#ifndef Tomato_OXFUNCTIONST1ThreeParams_HXX
#define Tomato_OXFUNCTIONST1ThreeParams_HXX
namespace Ox {
template< typename MeasureType >
MeasureType
FunctionsT1ThreeParam<MeasureType>
::calcModelValue(const MeasureType* parameters, MeasureType time){
MeasureType A = parameters[0];
MeasureType B = parameters[1];
MeasureType T1star = parameters[2];
if (fabs(T1star) < std::numeric_limits<MeasureType>::min())
return A;
return A - B * exp( -time / T1star );
}
template< typename MeasureType >
void
FunctionsT1ThreeParam<MeasureType>
::calcLSResiduals(const MeasureType* parameters, MeasureType* residuals){
unsigned int nSamples = this->_nSamples;
for (unsigned int i = 0; i < nSamples; i++) {
MeasureType invTime = this->_InvTimes[i];
MeasureType measured = this->_Signal[i];
MeasureType calculated = 0;
calculated = calcModelValue(parameters, invTime);
residuals[i] = calculated - measured;
}
}
template< typename MeasureType >
void
FunctionsT1ThreeParam<MeasureType>
::calcLSJacobian(const MeasureType* parameters, MeasureType* jacobian){
int nSamples = this->_nSamples;
//MeasureType A = parameters[0];
MeasureType B = parameters[1];
MeasureType T1star = parameters[2];
MeasureType invTime, myexp;
for (int i = 0; i < nSamples; i++) {
invTime = this->_InvTimes[i];
myexp = exp(-invTime/T1star);
// calculated in matlab (syms A B T1 t), f=A-B*exp(-t./T1); diff(f,A), diff(f,B), diff(f,T1)
jacobian[i*3+0] = 1.0;
jacobian[i*3+1] = -myexp;
jacobian[i*3+2] = -B * invTime * myexp / (T1star * T1star);
}
}
template< typename MeasureType >
MeasureType
FunctionsT1ThreeParam<MeasureType>
::calcCostValue(const MeasureType* parameters){
//std::cout << "calcCostValue" << std::endl;
int nSamples = this->_nSamples;
calcLSResiduals(parameters, this->_Residuals);
MeasureType result = 0;
for (int i = 0; i < nSamples; ++i) {
result = result + this->_Residuals[i] * this->_Residuals[i];
}
return result;
}
template< typename MeasureType >
void
FunctionsT1ThreeParam<MeasureType>
::calcCostDerivative(const MeasureType* parameters, MeasureType* derivative){
//std::cout << "calcCostDerivative" << std::endl;
int nSamples = this->_nSamples;
derivative[0] = 0;
derivative[1] = 0;
derivative[2] = 0;
MeasureType measured, invTime, myexp;
MeasureType A = parameters[0];
MeasureType B = parameters[1];
MeasureType T1star = parameters[2];
// calculated in matlab (syms A B T1 t y), f=(A-B*exp(-t./T1)-y).^2; diff(f,A), diff(f,B), diff(f,T1)
for (int i = 0; i < nSamples; ++i){
measured = this->getSignal()[i];
invTime = this->getInvTimes()[i];
myexp = exp(-invTime/T1star);
derivative[0] = derivative[0] + A*2 - measured*2 - myexp*B*2;;
derivative[1] = derivative[1] + myexp*2*(measured - A + myexp*B);
derivative[2] = derivative[2] + (invTime*myexp*B*2*(measured - A + myexp*B))/(T1star*T1star);
}
}
} //namespace Ox
#endif //Tomato_OXFUNCTIONST1ThreeParams_HXX