Python stats.density函数代码示例

def test_rademacher():
    X = Rademacher('X')

    assert E(X) == 0
    assert variance(X) == 1
    assert density(X)[-1] == S.Half
    assert density(X)[1] == S.Half

def test_discreteuniform():
    # Symbolic
    a, b, c, t = symbols('a b c t')
    X = DiscreteUniform('X', [a, b, c])

    assert E(X) == (a + b + c)/3
    assert simplify(variance(X)
                    - ((a**2 + b**2 + c**2)/3 - (a/3 + b/3 + c/3)**2)) == 0
    assert P(Eq(X, a)) == P(Eq(X, b)) == P(Eq(X, c)) == S('1/3')

    Y = DiscreteUniform('Y', range(-5, 5))

    # Numeric
    assert E(Y) == S('-1/2')
    assert variance(Y) == S('33/4')

    for x in range(-5, 5):
        assert P(Eq(Y, x)) == S('1/10')
        assert P(Y <= x) == S(x + 6)/10
        assert P(Y >= x) == S(5 - x)/10

    assert dict(density(Die('D', 6)).items()) == \
           dict(density(DiscreteUniform('U', range(1, 7))).items())

    assert characteristic_function(X)(t) == exp(I*a*t)/3 + exp(I*b*t)/3 + exp(I*c*t)/3
    assert moment_generating_function(X)(t) == exp(a*t)/3 + exp(b*t)/3 + exp(c*t)/3

def test_lognormal():
    mean = Symbol('mu', real=True, finite=True)
    std = Symbol('sigma', positive=True, real=True, finite=True)
    X = LogNormal('x', mean, std)
    # The sympy integrator can't do this too well
    #assert E(X) == exp(mean+std**2/2)
    #assert variance(X) == (exp(std**2)-1) * exp(2*mean + std**2)

    # Right now, only density function and sampling works
    # Test sampling: Only e^mean in sample std of 0
    for i in range(3):
        X = LogNormal('x', i, 0)
        assert S(sample(X)) == N(exp(i))
    # The sympy integrator can't do this too well
    #assert E(X) ==

    mu = Symbol("mu", real=True)
    sigma = Symbol("sigma", positive=True)

    X = LogNormal('x', mu, sigma)
    assert density(X)(x) == (sqrt(2)*exp(-(-mu + log(x))**2
                                    /(2*sigma**2))/(2*x*sqrt(pi)*sigma))

    X = LogNormal('x', 0, 1)  # Mean 0, standard deviation 1
    assert density(X)(x) == sqrt(2)*exp(-log(x)**2/2)/(2*x*sqrt(pi))

def test_multivariate_laplace():
    from sympy.stats.crv_types import Laplace
    raises(ValueError, lambda: Laplace('T', [1, 2], [[1, 2], [2, 1]]))
    L = Laplace('L', [1, 0], [[1, 2], [0, 1]])
    assert density(L)(2, 3) == exp(2)*besselk(0, sqrt(3))/pi
    L1 = Laplace('L1', [1, 2], [[x, 0], [0, y]])
    assert density(L1)(0, 1) == \
        exp(2/y)*besselk(0, sqrt((2 + 4/y + 1/x)/y))/(pi*sqrt(x*y))

def test_difficult_univariate():
    """ Since using solve in place of deltaintegrate we're able to perform
    substantially more complex density computations on single continuous random
    variables """
    x = Normal('x', 0, 1)
    assert density(x**3)
    assert density(exp(x**2))
    assert density(log(x))

def test_MultivariateTDist():
    from sympy.stats.joint_rv_types import MultivariateT
    t1 = MultivariateT('T', [0, 0], [[1, 0], [0, 1]], 2)
    assert(density(t1))(1, 1) == 1/(8*pi)
    assert integrate(density(t1)(x, y), (x, -oo, oo), \
        (y, -oo, oo)).evalf() == 1
    raises(ValueError, lambda: MultivariateT('T', [1, 2], [[1, 1], [1, -1]], 1))
    t2 = MultivariateT('t2', [1, 2], [[x, 0], [0, y]], 1)
    assert density(t2)(1, 2) == 1/(2*pi*sqrt(x*y))

def test_rademacher():
    X = Rademacher('X')
    t = Symbol('t')

    assert E(X) == 0
    assert variance(X) == 1
    assert density(X)[-1] == S.Half
    assert density(X)[1] == S.Half
    assert characteristic_function(X)(t) == exp(I*t)/2 + exp(-I*t)/2
    assert moment_generating_function(X)(t) == exp(t) / 2 + exp(-t) / 2

def test_conditional_1d():
    X = Normal('x', 0, 1)
    Y = given(X, X >= 0)

    assert density(Y) == 2 * density(X)

    assert Y.pspace.domain.set == Interval(0, oo)
    assert E(Y) == sqrt(2) / sqrt(pi)

    assert E(X**2) == E(Y**2)

def test_cauchy():
    x0 = Symbol("x0")
    gamma = Symbol("gamma", positive=True)

    X = Cauchy('x', x0, gamma)
    assert density(X)(x) == 1/(pi*gamma*(1 + (x - x0)**2/gamma**2))
    assert cdf(X)(x) == atan((x - x0)/gamma)/pi + S.Half
    assert diff(cdf(X)(x), x) == density(X)(x)

    gamma = Symbol("gamma", positive=False)
    raises(ValueError, lambda: Cauchy('x', x0, gamma))

def test_Normal():
    m = Normal('A', [1, 2], [[1, 0], [0, 1]])
    assert density(m)(1, 2) == 1/(2*pi)
    raises (ValueError,\
        lambda: Normal('M',[1, 2], [[0, 0], [0, 1]]))
    n = Normal('B', [1, 2, 3], [[1, 0, 0], [0, 1, 0], [0, 0, 1]])
    p = Normal('C',  Matrix([1, 2]), Matrix([[1, 0], [0, 1]]))
    assert density(m)(x, y) == density(p)(x, y)
    assert marginal_distribution(n, 0, 1)(1, 2) == 1/(2*pi)
    assert integrate(density(m)(x, y), (x, -oo, oo), (y, -oo, oo)).evalf() == 1
    N1 = Normal('N1', [1, 2], [[x, 0], [0, y]])
    assert str(density(N1)(0, 0)) == "exp(-(4*x + y)/(2*x*y))/(2*pi*sqrt(x*y))"

    raises (ValueError, lambda: Normal('M', [1, 2], [[1, 1], [1, -1]]))

def test_bernoulli():
    p, a, b = symbols('p a b')
    X = Bernoulli('B', p, a, b)

    assert E(X) == a*p + b*(-p + 1)
    assert density(X)[a] == p
    assert density(X)[b] == 1 - p

    X = Bernoulli('B', p, 1, 0)

    assert E(X) == p
    assert simplify(variance(X)) == p*(1 - p)
    E(a*X + b) == a*E(X) + b
    variance(a*X + b) == a**2 * variance(X)

def test_bernoulli():
    p, a, b = symbols("p a b")
    X = Bernoulli(p, a, b, symbol="B")

    assert E(X) == a * p + b * (-p + 1)
    assert density(X)[a] == p
    assert density(X)[b] == 1 - p

    X = Bernoulli(p, 1, 0, symbol="B")

    assert E(X) == p
    assert variance(X) == -p ** 2 + p
    E(a * X + b) == a * E(X) + b
    variance(a * X + b) == a ** 2 * variance(X)

def test_coins():
    C, D = Coin("C"), Coin("D")
    H, T = symbols("H, T")
    assert P(Eq(C, D)) == S.Half
    assert density(Tuple(C, D)) == {(H, H): S.One / 4, (H, T): S.One / 4, (T, H): S.One / 4, (T, T): S.One / 4}
    assert dict(density(C).items()) == {H: S.Half, T: S.Half}

    F = Coin("F", S.One / 10)
    assert P(Eq(F, H)) == S(1) / 10

    d = pspace(C).domain

    assert d.as_boolean() == Or(Eq(C.symbol, H), Eq(C.symbol, T))

    raises(ValueError, lambda: P(C > D))  # Can't intelligently compare H to T

def test_coins():
    C, D = Coin(), Coin()
    H, T = sorted(density(C).keys())
    assert P(Eq(C, D)) == S.Half
    assert density(Tuple(C, D)) == {(H, H): S.One / 4, (H, T): S.One / 4, (T, H): S.One / 4, (T, T): S.One / 4}
    assert density(C) == {H: S.Half, T: S.Half}

    E = Coin(S.One / 10)
    assert P(Eq(E, H)) == S(1) / 10

    d = pspace(C).domain

    assert d.as_boolean() == Or(Eq(C.symbol, H), Eq(C.symbol, T))

    raises(ValueError, lambda: P(C > D))  # Can't intelligently compare H to T

def test_uniformsum():
    n = Symbol("n", integer=True)
    _k = Symbol("k")

    X = UniformSum('x', n)
    assert density(X)(x) == (Sum((-1)**_k*(-_k + x)**(n - 1)
                        *binomial(n, _k), (_k, 0, floor(x)))/factorial(n - 1))