PolynomialUnivariate.cpp

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#include <iostream>
#include <cmath>

#include "PolynomialUnivariate.h"
#include "IString.h"
#include "IException.h"

namespace Isis {
  PolynomialUnivariate::PolynomialUnivariate(int degree) :
    Isis::Basis1VariableFunction("PolynomialUnivariate", (degree + 1)) {
    p_degree = degree;
  }


   PolynomialUnivariate::PolynomialUnivariate(int degree, std::vector<double> coeffs) :
    Isis::Basis1VariableFunction("PolynomialUnivariate", (degree + 1)) {
     p_degree = degree;
     SetCoefficients(coeffs);
   }


  void PolynomialUnivariate::Expand(const std::vector<double> &vars) {
    p_terms.clear();
    p_terms.push_back(1.0);

    for(int i = 1; i <= p_degree; i++) {
      p_terms.push_back(p_terms[i-1]*vars[0]);
    }
  }


  double PolynomialUnivariate::DerivativeVar(const double value) {

    double derivative = 0;

    for(int i = 1; i < Coefficients(); i++) {
      derivative += i * Coefficient(i) * pow(value, i - 1);
    }
    return derivative;
  }



  double PolynomialUnivariate::DerivativeCoef(const double value,
      const int coefIndex) {
    double derivative;

    if(coefIndex > 0  && coefIndex <= Coefficients()) {
      derivative = pow(value, coefIndex);
    }
    else if(coefIndex == 0) {
      derivative = 1;
    }
    else {
      QString msg = "Unable to evaluate the derivative of the univariate polynomial for the given "
                    "coefficient index [" + toString(coefIndex) + "]. "
                    "Index is negative or exceeds degree of polynomial ["
                    + toString(Coefficients()) + "]";
      throw IException(IException::Programmer, msg, _FILEINFO_);
    }
    return derivative;
  }


} // end namespace isis