// Prepare data.

int n = 5000;

Eigen::VectorXd x(n), y(n), z(n), w = 2 * Eigen::VectorXd::Ones(n);

for (int i = 0; i < n; ++i) {

x(i) = i * i;

y(i) = sin(2 * M_PI * i / 360.0);

z(i) = log(i);

}

// Set the size of output image = 1200x780 pixels

plt::figure_size(1200, 780);

// Plot line from given x and y data. Color is selected automatically.

plt::plot(x, y);

// Plot a red dashed line from given x and y data.

plt::plot(x, w, "r--");

// Plot a line whose name will show up as "log(x)" in the legend.

plt::plot(x, z, {{"label", "log(x)"}});

// Set x-axis to interval [0,1000000]

plt::xlim(0, 1000 * 1000);

// Add graph title

plt::title("Sample figure");

// Enable legend.

plt::legend();

// save figure

const char *filename = "./eigen_basic.png";

std::cout << "Saving result to " << filename << std::endl;

plt::savefig(filename);