public static void GaussianElimination(BGeomMatrix matrix, Vector rhs, ref double[] results)
{
// Create augmented matrix
var augmentedElements = new List<List<double>>();
for (var i = 0; i < matrix.GetNRows(); i++)
{
augmentedElements.Add(new List<double>());
for (var j = 0; j < matrix.GetNColumns(); j++)
augmentedElements[i].Add(matrix.GetElement(i, j));
augmentedElements[i].Add(rhs.Elements[i]);
}
// Create new matrix:
var augmentedMatrix = new BGeomMatrix(augmentedElements);
// Divide first row by the first element:
var pivot = augmentedMatrix.GetElement(0, 0);
if (TolerantUtilities.EqualWithinTol(pivot, 0.0))
throw new Exception("Cannot solve this type of matrix yet");
var row1 = augmentedMatrix.GetRow(0);
row1.ScalarProduct(1.0 / pivot);
// Now replace:
augmentedMatrix.ReplaceRow(0, row1);
var nRows = augmentedMatrix.GetNRows();
// Now enter loop
for (var i = 1; i < nRows; i++)
{
for (var j = 0; j < i; j++)
{
// get the jth row and multiply it with the ith row coefficient:
row1 = augmentedMatrix.GetRow(j);
// get coefficient:
var coefficient = augmentedMatrix.GetElement(i, j);
// Multiply:
row1.ScalarProduct(coefficient);
// Get the ith row:
var row2 = augmentedMatrix.GetRow(i);
// Subtract:
var rowSubs = row2 - row1;
// Make the first non-zero coeff 1.0:
coefficient = rowSubs.Elements[j+1];
rowSubs.ScalarProduct(1.0 / coefficient);
// Replace
augmentedMatrix.ReplaceRow(i, rowSubs);
}
}
// Now back substitution
var backSubs = new double[nRows];
// Fill in the last element:
backSubs[nRows - 1] = augmentedMatrix.GetElement(nRows-1, nRows);
// Starting from before last, start filling up:
for (var i = nRows - 2; i >= 0; i--)
{
// Get all the factors on the rhs:
var rhsFactors = 0.0;
for (var j = nRows - 1; j > i; j--)
rhsFactors += augmentedMatrix.GetElement(i, j)*backSubs[j];
// Now subtract:
backSubs[i] = augmentedMatrix.GetElement(i, nRows) - rhsFactors;
}
results = backSubs;
}
public static void CentripetalMethod_createSplineByInterpolation(
int degree, Vector[] interpolationPoints, ref BCurve result)
{
// NOTE: result is equal to null(ArgumentNullException)
// Calculate interpolation parameters:
double[] interpolationParameters = null;
CentripetalMethod_calculateInterpolationParameters(interpolationPoints, ref interpolationParameters);
// Calculate knots:
double[] knots = null;
CentripetalMethod_calculateKnots(degree, interpolationParameters, ref knots);
// Create basis function:
var basis = new BasisFunction(knots);
// Number of control points:
var nControlPoints = interpolationPoints.Length;
// Create set of linearly independent equations:
var matrixElements = new double[nControlPoints][];
for (var i = 0; i < nControlPoints; i++)
{
matrixElements[i] = new double[nControlPoints];
for (var j = 0; j < nControlPoints; j++)
matrixElements[i][j] = basis.Evaluate(j, degree, interpolationParameters[i]);
}
// Create matrix:
var matrix = new BGeomMatrix(matrixElements);
var dimension = interpolationPoints[0].VectorDimension();
// Solve using Gaussian Elimination:
var rhs = new Vector(nControlPoints);
var controlPoints = new Vector[nControlPoints];
for (var i = 0; i < dimension; i++)
{
// Fill the elements of the rhs:
for (var j = 0; j < nControlPoints; j++)
rhs.Elements[j] = interpolationPoints[j].Elements[i];
double[] gaussResult = null;
LinearAlgebra.GaussianElimination(matrix, rhs, ref gaussResult);
// Fill the control points
for (var k = 0; k < nControlPoints; k++)
{
if ( i == 0)
controlPoints[k] = new Vector(dimension);
controlPoints[k].Elements[i] = gaussResult[k];
}
}
// Create spline:
result = new BCurve(degree, controlPoints, basis);
}
private void button1_Click(object sender, EventArgs e)
{
var knots = new List<double>
{
0.0,
0.0,
0.0,
1.0,
2.0,
3.0,
4.0,
4.0,
5.0,
5.0,
5.0
};
var controlPoints = new List<Vector>
{
new Vector(new[] {0.0, 0.0}),
new Vector(new[] {1.0, 1.0}),
new Vector(new[] {2.0, 0.0}),
new Vector(new[] {3.0, -1.0}),
new Vector(new[] {4.0, 0.0}),
new Vector(new[] {5.0, 1.0}),
new Vector(new[] {6.0, 0.0}),
new Vector(new[] {7.0, -1.0})
};
var basis = new BasisFunction(knots);
var curve = new BCurve(2, controlPoints, basis);
_sessionCurve = curve;
curve.Evaluate(2.5);
// Testing gaussian elimination:
var matrixElements = new List<List<double>>
{
new List<double>
{
1,
-3,
1
},
new List<double>
{
2,
-8,
8
},
new List<double>
{
-6,
3,
-15
}
};
var rhs = new Vector(new double[] { 4, -2, 9 });
var matrix = new BGeomMatrix(matrixElements);
double[] results = null;
LinearAlgebra.GaussianElimination(matrix, rhs, ref results);
// make straight line with points:
var straightLine0 = new List<Vector>();
for (var i = 0; i < 5; i++)
straightLine0.Add(new Vector(new[] { i, i % 2.0 }));
// Interpolate straight line
var straightLine1 = new BCurve();
GeomUtils.CentripetalMethod_createSplineByInterpolation(3, straightLine0.ToArray(), ref straightLine1);
_sessionCurve = straightLine1;
}