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/*
File : FourierTransformTest.cpp
Project : LabPlot
Description : Tests for discrete Fourier transformation
--------------------------------------------------------------------
SPDX-FileCopyrightText: 2024 Martin Marmsoler <martin.marmsoler@gmail.com>
SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "FourierTransformTest.h"
#include "backend/core/column/Column.h"
#include "backend/worksheet/plots/cartesian/XYFourierTransformCurve.h"
#include <iostream>
// #include <math.h>
// ##############################################################################
// https://de.mathworks.com/help/matlab/ref/fft.html
void FourierTransformTest::fft() {
constexpr int length_signal = 1500;
constexpr double fs = 1000.0; // [Hz]
// data
QVector<double> time(length_signal);
QVector<double> yData(length_signal);
for (size_t i = 0; i < length_signal; i++) {
const auto t = (double)i / fs;
time[i] = t;
yData[i] = 0.8 + 0.7 * sin(2.0 * M_PI * 50.0 * t) + sin(2.0 * M_PI * 120.0 * t);
}
// data source columns
Column xDataColumn(QStringLiteral("time"), AbstractColumn::ColumnMode::Double);
xDataColumn.replaceValues(0, time);
Column yDataColumn(QStringLiteral("y"), AbstractColumn::ColumnMode::Double);
yDataColumn.replaceValues(0, yData);
XYFourierTransformCurve curve(QStringLiteral("fourier transform"));
curve.setXDataColumn(&xDataColumn);
curve.setYDataColumn(&yDataColumn);
// prepare the fourier transform data
auto data = curve.transformData();
QCOMPARE(data.type, nsl_dft_result_amplitude);
curve.setTransformData(data);
// perform the calculation
curve.recalculate();
const auto& result = curve.result();
// check the results
QCOMPARE(result.available, true);
QCOMPARE(result.valid, true);
const auto* resultXDataColumn = curve.xColumn();
const auto* resultYDataColumn = curve.yColumn();
const int np = resultXDataColumn->rowCount();
QCOMPARE(np, length_signal / 2);
for (int i = 0; i < np; i++) {
const auto x = resultXDataColumn->valueAt(i);
auto y = resultYDataColumn->valueAt(i);
// std::cout << i << ", x: " << x << ", y: " << std::endl;
// Three peaks:
// - first at zero
// - second at 50Hz
// - third at 120Hz
if (x == 0)
VALUES_EQUAL(y, 0.8);
else if (x == 50)
VALUES_EQUAL(y, 0.7);
else if (x == 120)
VALUES_EQUAL(y, 1.0);
else
QVERIFY(std::abs(y) < 1e-12);
}
}
QTEST_MAIN(FourierTransformTest)
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