still only third order, but with possibility to get values from approximation

include/ITABase/Spline.h

@@ -52,6 +52,8 @@ namespace ITABase
 
 		//! Evaluate the piecewise polynomial at a given x value.
 		float Value(const float xValue) const;
+		//! Finds the index of Interval at a given x value
+		int IntervalIndex(const float xValue) const;
 		//! Return a piecewise polynomial containing the derivations of the polynomials of this one
 		CPiecewisePolynomial Derivation() const;
 

src/ITABase/Spline.cpp

@@ -3,6 +3,7 @@
 
 #include <string>
 #include <algorithm>
+#include <cmath>
 
 using namespace ITABase;
 
@@ -26,18 +27,27 @@ CPiecewisePolynomial::CPiecewisePolynomial(const std::vector<float>& vdBreakPoin
 
 float CPiecewisePolynomial::Value(const float xValue) const
 {
-	//TODO: Check if x-value is inside boundaries
-
-	//TODO: Find index of interval, get corresponding coefficients and calculate values
+	// Check if x-value is inside boundaries
+	// Find index of interval
+	int iInterval = IntervalIndex(xValue);
+	//TODO: get corresponding coefficients and calculate values
+	std::vector<float>::const_iterator itCoef = CoefficientsOfInterval(iInterval);
+	//f(x) = a1(x−x1)^3 + b1(x−x1)^2 + c1(x−x1) + d1
+	float x0 = vdBreakPoints[iInterval];
+	if (iOrder == 3)
+		return itCoef[0] * pow(xValue - x0, 3) + itCoef[1] * pow(xValue - x0, 2) + itCoef[2] * (xValue - x0) + itCoef[3];
+	else
+		ITA_EXCEPT_INVALID_PARAMETER("currently only splines of order 3");
+}
 
-	//Something like this might be necessary
-	std::vector<float>::const_iterator itStart = CoefficientsOfInterval(0);
-	std::vector<float>::const_iterator itEnd = itStart + NumCoefficients();
-	for (std::vector<float>::const_iterator it = itStart; itStart < itEnd; it++)
-	{
+int ITABase::CPiecewisePolynomial::IntervalIndex(const float xValue) const
+{
+	if (xValue < vdBreakPoints[0] || xValue > vdBreakPoints[NumIntervals()])
+		ITA_EXCEPT_INVALID_PARAMETER("xValue is out of bounds");
+	for (int i = 1; i < vdBreakPoints.size(); i++) {
+		if (vdBreakPoints[i] > xValue)
+			return i - 1;
 	}
-
-	return 0.0;
 }
 
 CPiecewisePolynomial CPiecewisePolynomial::Derivation() const
@@ -80,12 +90,15 @@ CPiecewisePolynomial ITABase::Spline(const std::vector<float>& vdSupportingPoint
 	https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjcofWO_IrqAhUux4sKHT52AigQFjABegQIBRAB&url=http%3A%2F
 	out of the b vector.
 	*/
+	if (vdSupportingPoints.size()!= vdDataPoints.size())
+		ITA_EXCEPT_INVALID_PARAMETER("vdSupportingPoints and vdDataPoints need to have the same size");
+	//TODO andere als Ordnung 3
 
-	//Calculate h_i
+	//Calculate h_i, formular 1.27b
 	int iPoints = vdSupportingPoints.size();
 	std::vector<float> vdH(iPoints-1);
 	
-	for (int i = 0; i < iPoints-1; i++) {//TODO needs tp be positiv
+	for (int i = 0; i < iPoints-1; i++) {
 		vdH[i] = vdSupportingPoints[i + 1] - vdSupportingPoints[i];
 		if (vdH[i] < 0) {
 			ITA_EXCEPT_INVALID_PARAMETER("vdSupportingPoints needs to be sorted in ascending order");
@@ -106,11 +119,10 @@ CPiecewisePolynomial ITABase::Spline(const std::vector<float>& vdSupportingPoint
 	//excitation vector
 	//TODO only for natural splines with S0=S_iPoints = 0
 	std::vector<float> vdR(iPoints - 2);
-	for (int i = 0; i < iPoints - 2; i++) {
-		vdR[i] = (vdDataPoints[i + 2] - vdDataPoints[i + 1]) / vdH[i + 1] - (vdDataPoints[i + 1] - vdDataPoints[i]) / vdH[i];
-		vdR[i] *= 3;
-	}
-	
+	for (int i = 0; i < iPoints - 2; i++) 
+		vdR[i] = 3 *( (vdDataPoints[i + 2] - vdDataPoints[i + 1]) / vdH[i + 1] - (vdDataPoints[i + 1] - vdDataPoints[i]) / vdH[i]);
+
+	//TODO auslagern
 	//solving bandmatrix with "numerical recipees in C" page 51
 	//if (vdMiddle[0] == 0)
 	//ITA_EXCEPT_INVALID_PARAMETER("Matrix needs to be semi positiv definit.");
@@ -148,13 +160,11 @@ CPiecewisePolynomial ITABase::Spline(const std::vector<float>& vdSupportingPoint
 	int iCoefficients = (iPoints - 1) * (iPolynomialOrder + 1);
 	std::vector<float> vdCoefficients(iCoefficients);
 	int k = 0;
-	for (int i = 0; i < iCoefficients;) {
-		vdCoefficients[i] = vdA[k];
-		vdCoefficients[i + 1] = vdB[k];
-		vdCoefficients[i + 2] = vdC[k];
-		vdCoefficients[i + 3] = vdD[k];
-		i += 4;
-		k += 1;
+	for (int k = 0; k < iPolynomialOrder + 1;k++) {
+		vdCoefficients[4*k] = vdA[k];
+		vdCoefficients[4*k + 1] = vdB[k];
+		vdCoefficients[4*k + 2] = vdC[k];
+		vdCoefficients[4*k + 3] = vdD[k];
 	}
 
 	return CPiecewisePolynomial(vdSupportingPoints, vdCoefficients, iPolynomialOrder);

tests/SplineTest.cpp

@@ -32,7 +32,7 @@ int main(int iNumInArgs, char* pcInArgs[])
 	//std::vector<float> vdSolution{ -0.01045, 0, 0.7091, 8, 0.0304, -1.88185, -0.4194, 10, -0.05005, 0.268014, -0.02026, 7, 0.01520, -0.182432, 0.2365, 8 };
 	int iPolynomialOrder = 3;
 	IW_ITA_BASE_SPLINE::ITABase::CPiecewisePolynomial myPoly = IW_ITA_BASE_SPLINE::ITABase::Spline(vdSupportingPoints,vdDataPoints,iPolynomialOrder);
-	
+	std::cout << "Quick and dirty test: "<< myPoly.Value(5)<<" -hier soll grob 10 rauskommen;)";
 
 	/*for (int i=0; it < vdDataPoints.size(); i++) {
 		std::cout << vdSolution[i] - myPoly.get_Coefficient(i);