public void Test_FastFourierTransform_BasicInput()
{
var inputSample = new[]
{
new Complex(1, 0),
new Complex(1, 0),
new Complex(1, 0),
new Complex(1, 0),
new Complex(1, 0),
new Complex(1, 0),
new Complex(1, 0),
new Complex(1, 0)
};
FourierTransforms.FastFourierTransform(inputSample, 0, inputSample.Length);
var expectedResult = new[]
{
new Complex(8, 0),
new Complex(0, 0),
new Complex(0, 0),
new Complex(0, 0),
new Complex(0, 0),
new Complex(0, 0),
new Complex(0, 0),
new Complex(0, 0)
};
Assert.IsTrue(inputSample.SequenceEqual(expectedResult));
}
public void Test_FastFourierTransform_SeparateSizeIsSmallerThan2()
{
var inputSample = new[] { new Complex(0, 0) };
FourierTransforms.FastFourierTransform(inputSample, 0, 1);
Assert.IsTrue(inputSample.SequenceEqual(new Complex[] { new Complex(0, 0) }));
}
public void Test_FastFourierTransform_InputSamplesNotPowerOfTwo()
{
var inputSample = new Complex[8];
Assert.Throws <ArgumentException>(
() => FourierTransforms.FastFourierTransform(inputSample, 0, 10),
"the number of inputSamples must be power of 2");
}
public void Test_FFT_VS_DFT()
{
var csvFilePath = Path.Combine(
TestContext.CurrentContext.TestDirectory,
@"TestData\Wave000.csv");
var inputSamplesList = CSVUtils.ReadCSVFile <CSVWaveRecord>(csvFilePath);
var dftInputArray = inputSamplesList.Select(x => new Complex((double)x.Volts, 0)).ToArray();
Utils.PadWithZeros(inputSamplesList);
var fftInputArray = inputSamplesList.Select(x => new Complex((double)x.Volts, 0)).ToArray();
FourierTransforms.DiscreteFourierTransform(dftInputArray);
FourierTransforms.FastFourierTransform(fftInputArray, 0, fftInputArray.Length);
}
public void Test_FastFourierTransform_Abraham()
{
var inputSample = new[]
{
new Complex(1, 0),
new Complex(2, 0),
new Complex(3, 0),
new Complex(4, 0),
};
FourierTransforms.FastFourierTransform(inputSample, 0, inputSample.Length);
var expectedResult = new[]
{
new Complex(10, 0),
new Complex(-2, 2),
new Complex(-2, 0),
new Complex(-1.9999999999999998, -2)
};
Assert.IsTrue(inputSample.SequenceEqual(expectedResult));
}
static LinkedList <FrequencyMagnitude> FFT(string filePath, string ouputDirectoryPath)
{
var inputSamplesList = CSVUtils.ReadCSVFile <CSVWaveRecord>(filePath);
Utils.PadWithZeros(inputSamplesList);
var frequencyResolution = Utils.CalculateFrequencyResolution(inputSamplesList);
var inputSamplesArray = inputSamplesList.Select(x => new Complex((double)x.Volts, 0)).ToArray();
FourierTransforms.FastFourierTransform(inputSamplesArray, 0, inputSamplesArray.Length);
var size = inputSamplesArray.Length / 2;
var leftHalfArray = new Complex[size];
Array.Copy(inputSamplesArray, leftHalfArray, size);
inputSamplesArray = null;
var intermediateFilePath = Path.Combine(ouputDirectoryPath,
Path.GetFileName(filePath).Replace("Wave", "FFT"));
Utils.printOutput(leftHalfArray, frequencyResolution, intermediateFilePath);
return(Utils.GetFrequencyDomain(leftHalfArray, frequencyResolution));
}