public void Test_Separate_First_Half_Array()
{
var inputSample = new[]
{
new Complex(0, 0),
new Complex(1, 0),
new Complex(2, 0),
new Complex(3, 0),
new Complex(4, 0),
new Complex(5, 0),
new Complex(6, 0),
new Complex(7, 0)
};
FourierTransforms.Separate(inputSample, 0, 4);
var expectedResult = new[]
{
new Complex(0, 0),
new Complex(2, 0),
new Complex(1, 0),
new Complex(3, 0),
new Complex(4, 0),
new Complex(5, 0),
new Complex(6, 0),
new Complex(7, 0)
};
Assert.IsTrue(inputSample.SequenceEqual(expectedResult));
}
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);
}
}
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) }));
}
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_Separate_SeparateSizeNotPowerOfTwo()
{
var inputSample = Enumerable.Range(0, 16).Select(i => (Complex)i).ToArray();
Assert.Throws <ArgumentException>(
() => FourierTransforms.Separate(inputSample, 0, 15),
"size must be power of 2");
}
public void Test_Separate_StartIndexPlusSizeIsGreaterThanArraySize()
{
var inputSample = Enumerable.Range(0, 16).Select(i => (Complex)i).ToArray();
Assert.Throws <IndexOutOfRangeException>(
() => FourierTransforms.Separate(inputSample, 1, 16),
"startIndex + size is too large for array 'inputSamples'");
}
public void Test_Separate_StartIndexSmallerThanZero()
{
var inputSample = Enumerable.Range(0, 16).Select(i => (Complex)i).ToArray();
Assert.Throws <IndexOutOfRangeException>(
() => FourierTransforms.Separate(inputSample, -5, 16),
"startIndex must be greater than or equal to zero");
}
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_Separate_Entire_Array()
{
var inputSize = 16;
var inputSample = Enumerable.Range(0, inputSize).Select(i => (Complex)i).ToArray();
FourierTransforms.Separate(inputSample, 0, inputSize);
var evenIndexies = Enumerable.Range(0, inputSize)
.Where((x, i) => i % 2 == 0)
.Select(x => (Complex)x);
var oddIndexies = Enumerable.Range(0, inputSize)
.Where((x, i) => i % 2 != 0)
.Select(x => (Complex)x);
var expectedResult = evenIndexies.Concat(oddIndexies).ToArray();
Assert.IsTrue(inputSample.SequenceEqual(expectedResult));
}
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));
}