public Canvas canvas() {
        Canvas canvas = new Canvas(getLowerBound(), getUpperBound());
        canvas.add(this);
        if (name != null) {
            canvas.setTitle(name);
        }
        return canvas;
    }
@Test
    public void testSparseMatrix() throws Exception {
        System.out.println("Sparse Matrix");

        var sparse = SparseMatrix.text(Paths.getTestData("matrix/mesh2em5.txt"));
        var canvas = SparseMatrixPlot.of(sparse).canvas();
        canvas.setTitle("mesh2em5");
        canvas.window();
    }