e_system(name);
    update_matrix(name);
}

function init_plot_named(name) {
    plot = document.getElementById(name);
    var canvas_rect = plot.getBoundingClientRect();
    invalidate_plot_named(name);

    plot.addEventListener('mousemove', function(e){
       var canvas_rect = plot.getBoundingClientRect();
       draw_plot_named(name, e.clientX - canvas_rect.left, e.clientY - canvas_rect.top, true);
       if(e.buttons == 1){
           invalidate_plot_named(name);
       } else if(e.buttons == 0){
    