public void Test_DiscreteFourierTransform()
{
var inputSample = new[]
{
new Complex(1, 0),
new Complex(2, 0),
new Complex(3, 0),
new Complex(4, 0)
};
var result = FourierTransforms.DiscreteFourierTransform(inputSample);
var expectedResult = new[]
{
new Complex(10, 0),
new Complex(-2, 2),
new Complex(-2, 0),
new Complex(-2, -2)
};
for (int i = 0; i < result.Length; i++)
{
var r = result[i];
var er = expectedResult[i];
var difference = 1E-10;
Assert.IsTrue(Math.Abs(r.Real - er.Real) <= difference);
Assert.IsTrue(Math.Abs(r.Imaginary - er.Imaginary) <= difference);
}
}
static LinkedList <FrequencyMagnitude> DFT(string filePath, string ouputDirectoryPath)
{
var inputSamplesList = CSVUtils.ReadCSVFile <CSVWaveRecord>(filePath);
if (ZeroPadDFT)
{
Utils.PadWithZeros(inputSamplesList);
}
var frequencyResolution = Utils.CalculateFrequencyResolution(inputSamplesList);
var inputSamplesArray = inputSamplesList.Select(x => new Complex((double)x.Volts, 0)).ToArray();
var dftValues = FourierTransforms.DiscreteFourierTransform(inputSamplesArray);
inputSamplesArray = null;
var size = dftValues.Length / 2;
var leftHalfArray = new Complex[size];
Array.Copy(dftValues, leftHalfArray, size);
dftValues = null;
var intermediateFile = Path.Combine(ouputDirectoryPath,
Path.GetFileName(filePath).Replace("Wave", "DFT"));
Utils.printOutput(leftHalfArray, frequencyResolution, intermediateFile);
return(Utils.GetFrequencyDomain(leftHalfArray, frequencyResolution));
}
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);
}