Scatter Plot

Render a 2D scatter plot of discrete data points. Uses the same rendering pipeline as line plots with point topology.

API

template <typename DerivedX, typename DerivedY>
void PlotView::scatter(const Eigen::MatrixBase<DerivedX>& x,
                       const Eigen::MatrixBase<DerivedY>& y);

Methods

Method	Description
scatter(x, y)	Set scatter data from two equal-length vectors
setLineColor(rgba)	Set point colour as Eigen::Vector4f
setBackgroundColor(rgba)	Set viewport background colour

Example

#include <skigen/plot/plotview.h>
#include <Eigen/Core>
#include <QApplication>
#include <random>

int main(int argc, char* argv[]) {
    QApplication app(argc, argv);

    std::mt19937 rng(42);
    std::normal_distribution<float> dist(0.f, 1.f);

    int n = 200;
    Eigen::VectorXf x(n), y(n);
    for (int i = 0; i < n; ++i) {
        x(i) = dist(rng);
        y(i) = dist(rng);
    }

    Skigen::Plot::PlotView view;
    view.scatter(x, y);
    view.setLineColor({1.0f, 0.4f, 0.3f, 1.0f});
    view.resize(600, 600);
    view.show();

    return app.exec();
}

Use with Skigen ML

Scatter plots are ideal for visualizing ML results — cluster assignments, PCA projections, decision boundaries:

// After PCA with Skigen
Skigen::PCA<double> pca(2);
Eigen::MatrixXd Z = pca.fit_transform(X);

view.scatter(Z.col(0).cast<float>(), Z.col(1).cast<float>());