private static IInvFourierTransformer CreateIft()
{
return(new InvFourierTransformer((coeffs, nodes) =>
{
var sobCosSystem = new SobolevCosSystem();
var sobolevPartSum = new FourierDiscretePartialSum(nodes,
Natural.NumbersWithZero.Select(k => sobCosSystem.Get(k)).Take(coeffs.Length).ToArray());
return sobolevPartSum.GetValues(coeffs).Y;
}));
}
public void GetValuesTest()
{
var basis = new Func <double, double>[]
{
x => 1,
x => x,
Cos,
};
var nodes = new[] { 0, PI / 6, PI / 4, PI / 3, PI / 2 };
var partSum = new FourierDiscretePartialSum(nodes, basis);
var df = partSum.GetValues(0, 0, 0);
Assert.AreEqual(nodes, df.X);
Assert.AreEqual(new[] { 0d, 0, 0, 0, 0 }, df.Y);
df = partSum.GetValues(1, 2, 0);
Assert.AreEqual(nodes, df.X);
Assert.AreEqual(nodes.Select(t => 1 + 2 * t).ToArray(), df.Y);
df = partSum.GetValues(1, 2, 3);
Assert.AreEqual(nodes, df.X);
Assert.AreEqual(nodes.Select(t => 1 + 2 * t + 3 * Cos(t)).ToArray(), df.Y);
}