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Added function selection in interpolation example #75

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Merged
pasabanov merged 1 commit into from
Sep 6, 2026
Merged

Added function selection in interpolation example #75

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60 changes: 42 additions & 18 deletions examples/interpolation/interpolation.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,25 +9,37 @@ QVector<T> to_qvector(const std::vector<T>& v) {
return QVector<T>(v.begin(), v.end());
}

double f(double x) {
// return -3 * std::sin(10 * x) + std::abs(x) + 0.5 * x - x * x; // example 1
return -3 * std::sin(10 * x) + 10 * std::sin(std::abs(x) + 0.5 * x); // example 2
// return std::sin(3 * M_PI * x) + std::cos(M_PI * x / 5); // periodic
// return 1/(1+std::exp(-10000*(x-1))) - 1/(1+std::exp(-10000*(x+1))); // high local second derivative
}

template <typename Container>
Container f(const Container& X) {
Container Y;
Y.reserve(X.size());
for (const auto& x : X) {
Y.push_back(f(x));
}
return Y;
template <typename F, typename Container>
Container eval_function(const F& function, const Container& xx) {
const auto transformed = xx | std::views::transform(function);
return Container(transformed.begin(), transformed.end());
}

class PlotWindow final : public QWidget {
public:
static const inline std::vector<std::pair<QString,std::function<std::vector<double>(std::vector<double>)>>>
functions = {
{"sin(x)", [](const auto& xx) {
return eval_function([](auto x) { return std::sin(x); }, xx);
}},
{"exp(x)", [](const auto& xx) {
return eval_function([](auto x) { return std::exp(x); }, xx);
}},
{"sin(3πx) + cos(πx/5)", [](const auto& xx) {
return eval_function([](auto x) { return std::sin(3 * M_PI * x) + std::cos(M_PI * x / 5); }, xx);
}},
{"-3sin(10x) + abs(x) + x/2 - x^2", [](const auto& xx) {
return eval_function([](auto x) { return -3 * std::sin(10 * x) + std::abs(x) + 0.5 * x - x * x; }, xx);
}},
{"-3sin(10x) + 10sin(abs(x) + x/2)", [](const auto& xx) {
return eval_function([](auto x) { return -3 * std::sin(10 * x) + 10 * std::sin(std::abs(x) + 0.5 * x); }, xx);
}},
{"1/(1 + exp(-10000(x-1))) - 1/(1 + exp(-10000(x+1)))", [](const auto& xx) {
return eval_function([](auto x) { return 1/(1+std::exp(-10000*(x-1))) - 1/(1+std::exp(-10000*(x+1))); }, xx);
}},
};
static const inline size_t function_default_index = 0;

static const inline std::vector<std::pair<QString,std::function<std::vector<double>(std::vector<double>,std::vector<double>,std::vector<double>)>>>
poly_types = {
{"Lagrange", [](const auto& X, const auto& Y, const auto& xx) { return alfi::poly::val(alfi::poly::lagrange(X, Y), xx); }},
Expand Down Expand Up @@ -148,6 +160,12 @@ class PlotWindow final : public QWidget {
_hermite_spline_checkbox = new QCheckBox("Hermite Spline");

_function_checkbox->setChecked(true);
_function_combo = new QComboBox();
for (const auto& name : functions | std::views::keys) {
_function_combo->addItem(name);
}
_function_combo->setCurrentIndex(function_default_index);

_points_checkbox->setChecked(true);

_poly_combo = new QComboBox();
Expand Down Expand Up @@ -203,10 +221,14 @@ class PlotWindow final : public QWidget {
connect(checkbox, &QCheckBox::toggled, this, &PlotWindow::update_plot);
}

for (const auto combo : {_distribution_combo, _poly_combo, _barycentric_combo, _step_spline_combo, _quadratic_spline_combo, _cubic_spline_combo, _hermite_spline_combo, _hermite_spline_boundaries_combo}) {
for (const auto combo : {_distribution_combo, _function_combo, _poly_combo, _barycentric_combo, _step_spline_combo, _quadratic_spline_combo, _cubic_spline_combo, _hermite_spline_combo, _hermite_spline_boundaries_combo}) {
connect(combo, QOverload<int>::of(&QComboBox::currentIndexChanged), this, &PlotWindow::update_plot);
}

connect(_function_combo, QOverload<int>::of(&QComboBox::currentIndexChanged), this, [this](int) {
_default_axis_ranges = true;
update_plot();
});
connect(_view_reset_button, &QPushButton::clicked, this, [this]() {
_default_axis_ranges = true;
update_plot();
Expand Down Expand Up @@ -243,6 +265,7 @@ class PlotWindow final : public QWidget {
// ReSharper disable once CppDFAMemoryLeak
QVBoxLayout* interpolation_layout = new QVBoxLayout();
interpolation_layout->addWidget(_function_checkbox);
interpolation_layout->addWidget(_function_combo);
interpolation_layout->addWidget(_points_checkbox);
interpolation_layout->addWidget(_poly_checkbox);
interpolation_layout->addWidget(_poly_combo);
Expand Down Expand Up @@ -340,7 +363,7 @@ class PlotWindow final : public QWidget {
default: return;
}

const auto Y = f(X);
const auto Y = functions[_function_combo->currentIndex()].second(X);

const std::vector<double> xx = alfi::dist::uniform(nn, a, b);

Expand Down Expand Up @@ -368,7 +391,7 @@ class PlotWindow final : public QWidget {
};

if (_function_checkbox->isChecked()) {
const auto yy = f(xx);
const auto yy = functions[_function_combo->currentIndex()].second(xx);
y_min = std::min(y_min, *std::ranges::min_element(yy));
y_max = std::max(y_max, *std::ranges::max_element(yy));
add_graph("Function", xx, yy);
Expand Down Expand Up @@ -441,6 +464,7 @@ class PlotWindow final : public QWidget {
QCheckBox* _cubic_spline_checkbox;
QCheckBox* _hermite_spline_checkbox;
QComboBox* _distribution_combo;
QComboBox* _function_combo;
QComboBox* _poly_combo;
QComboBox* _barycentric_combo;
QComboBox* _step_spline_combo;
Expand Down
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