@Override
    public double logp(double x) {
        return Math.log(p(x));
    }
@Test
    public void testLogp() {
        System.out.println("logp");
        KernelDensity instance = new KernelDensity(x);
        double expResult = -2.29044906;
        double result = instance.logp(3.5);
        assertEquals(expResult, result, 1E-8);
    }