Python numpy.correlate方法代码示例

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def _autocorr(data):
    """
    Calculates the auto correlation of a given array.

    Parameters
    ----------
    data : array-like
        The array to calculate the autocorrelation of

    Returns
    -------
    u : ndarray
        The array of autocorrelations
    """
    u = np.correlate(data, data, mode='full')
    # Take upper half of correlation matrix
    return u[u.size // 2:] 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def _presample_varcov(self, params):
        """
        Returns the inverse of the presample variance-covariance.

        Notes
        -----
        See Hamilton p. 125
        """
        k = self.k_trend
        p = self.k_ar
        p1 = p+1

        # get inv(Vp) Hamilton 5.3.7
        params0 = np.r_[-1, params[k:]]

        Vpinv = np.zeros((p, p), dtype=params.dtype)
        for i in range(1, p1):
            Vpinv[i-1, i-1:] = np.correlate(params0, params0[:i],)[:-1]
            Vpinv[i-1, i-1:] -= np.correlate(params0[-i:], params0,)[:-1]

        Vpinv = Vpinv + Vpinv.T - np.diag(Vpinv.diagonal())
        return Vpinv 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def ar_generator(N=512, sigma=1.):
    # this generates a signal u(n) = a1*u(n-1) + a2*u(n-2) + ... + v(n)
    # where v(n) is a stationary stochastic process with zero mean
    # and variance = sigma
    # this sequence is shown to be estimated well by an order 8 AR system
    taps = np.array([2.7607, -3.8106, 2.6535, -0.9238])
    v = np.random.normal(size=N, scale=sigma**0.5)
    u = np.zeros(N)
    P = len(taps)
    for l in range(P):
        u[l] = v[l] + np.dot(u[:l][::-1], taps[:l])
    for l in range(P,N):
        u[l] = v[l] + np.dot(u[l-P:l][::-1], taps)
    return u, v, taps

#JP: small differences to using np.correlate, because assumes mean(s)=0
#    denominator is N, not N-k, biased estimator
#    misnomer: (biased) autocovariance not autocorrelation
#from nitime.utils 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def extractMseq(cover, stego, secret_length, m, tau=1):
	u"""Extract secret informations by spread spectrum using m-sequence.
	@param  cover         : cover data (2 dimensional np.ndarray)
	@param  stego         : stego data (2 dimension np.ndarray)
	@param  secret_length : length of secret information
	@param  m             : M-Sequence
	@param  tau           : embed shift interval
	@return secret        : extracted secret information
	"""

	cover = _image2vrctor(cover)
	stego = _image2vrctor(stego)

	m_length = len(m)

	data = stego - cover
	data = data[:m_length:tau]

	secret_data = correlate(m, data, cycle=CYCLE)
	center = ((m_length-1)*2+1)//2
	secret_data = secret_data[center:center+secret_length]
	secret_data = list(map(_checkData, secret_data))

	return secret_data 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_rank0(self, dt):
        a = np.array(np.random.randn()).astype(dt)
        a += 1j * np.array(np.random.randn()).astype(dt)
        b = np.array(np.random.randn()).astype(dt)
        b += 1j * np.array(np.random.randn()).astype(dt)

        y_r = (correlate(a.real, b.real)
               + correlate(a.imag, b.imag)).astype(dt)
        y_r += 1j * (-correlate(a.real, b.imag) + correlate(a.imag, b.real))

        y = correlate(a, b, 'full')
        assert_array_almost_equal(y, y_r, decimal=self.decimal(dt) - 1)
        assert_equal(y.dtype, dt)

        assert_equal(correlate([1], [2j]), correlate(1, 2j))
        assert_equal(correlate([2j], [3j]), correlate(2j, 3j))
        assert_equal(correlate([3j], [4]), correlate(3j, 4)) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_consistency_correlate_funcs(self):
        # Compare np.correlate, signal.correlate, signal.correlate2d
        a = np.arange(5)
        b = np.array([3.2, 1.4, 3])
        for mode in ['full', 'valid', 'same']:
            assert_almost_equal(np.correlate(a, b, mode=mode),
                                signal.correlate(a, b, mode=mode))
            assert_almost_equal(np.squeeze(signal.correlate2d([a], [b],
                                                              mode=mode)),
                                signal.correlate(a, b, mode=mode))

            # See gh-5897
            if mode == 'valid':
                assert_almost_equal(np.correlate(b, a, mode=mode),
                                    signal.correlate(b, a, mode=mode))
                assert_almost_equal(np.squeeze(signal.correlate2d([b], [a],
                                                                  mode=mode)),
                                    signal.correlate(b, a, mode=mode)) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_float(self):
        self._setup(float)
        z = np.correlate(self.x, self.y, 'full')
        assert_array_almost_equal(z, self.z1)
        z = np.correlate(self.x, self.y[:-1], 'full')
        assert_array_almost_equal(z, self.z1_4)
        z = np.correlate(self.y, self.x, 'full')
        assert_array_almost_equal(z, self.z2)
        z = np.correlate(self.x[::-1], self.y, 'full')
        assert_array_almost_equal(z, self.z1r)
        z = np.correlate(self.y, self.x[::-1], 'full')
        assert_array_almost_equal(z, self.z2r)
        z = np.correlate(self.xs, self.y, 'full')
        assert_array_almost_equal(z, self.zs) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_object(self):
        self._setup(Decimal)
        z = np.correlate(self.x, self.y, 'full')
        assert_array_almost_equal(z, self.z1)
        z = np.correlate(self.y, self.x, 'full')
        assert_array_almost_equal(z, self.z2) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_no_overwrite(self):
        d = np.ones(100)
        k = np.ones(3)
        np.correlate(d, k)
        assert_array_equal(d, np.ones(100))
        assert_array_equal(k, np.ones(3)) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_complex(self):
        x = np.array([1, 2, 3, 4+1j], dtype=complex)
        y = np.array([-1, -2j, 3+1j], dtype=complex)
        r_z = np.array([3-1j, 6, 8+1j, 11+5j, -5+8j, -4-1j], dtype=complex)
        r_z = r_z[::-1].conjugate()
        z = np.correlate(y, x, mode='full')
        assert_array_almost_equal(z, r_z) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def xcorr(x, y, maxlags=None):
    """Cross-correlation between two 1D signals of the same length."""
    ns = len(x)
    if len(y) != ns:
        raise ValueError("x and y should have the same length.")
    maxlags = maxlags or ns - 1
    return np.correlate(x, y, mode='full')[ns - 1 - maxlags:ns + maxlags] 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_float(self):
        self._setup(np.float)
        z = np.correlate(self.x, self.y, 'full')
        assert_array_almost_equal(z, self.z1)
        z = np.correlate(self.x, self.y[:-1], 'full')
        assert_array_almost_equal(z, self.z1_4)
        z = np.correlate(self.y, self.x, 'full')
        assert_array_almost_equal(z, self.z2)
        z = np.correlate(self.x[::-1], self.y, 'full')
        assert_array_almost_equal(z, self.z1r)
        z = np.correlate(self.y, self.x[::-1], 'full')
        assert_array_almost_equal(z, self.z2r)
        z = np.correlate(self.xs, self.y, 'full')
        assert_array_almost_equal(z, self.zs) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def test_complex(self):
        x = np.array([1, 2, 3, 4+1j], dtype=np.complex)
        y = np.array([-1, -2j, 3+1j], dtype=np.complex)
        r_z = np.array([3-1j, 6, 8+1j, 11+5j, -5+8j, -4-1j], dtype=np.complex)
        r_z = r_z[::-1].conjugate()
        z = np.correlate(y, x, mode='full')
        assert_array_almost_equal(z, r_z) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def ccf(x, y, unbiased=True):
    '''cross-correlation function for 1d

    Parameters
    ----------
    x, y : arrays
       time series data
    unbiased : boolean
       if True, then denominators for autocovariance is n-k, otherwise n

    Returns
    -------
    ccf : array
        cross-correlation function of x and y

    Notes
    -----
    This is based np.correlate which does full convolution. For very long time
    series it is recommended to use fft convolution instead.

    If unbiased is true, the denominator for the autocovariance is adjusted
    but the autocorrelation is not an unbiased estimtor.

    '''
    cvf = ccovf(x, y, unbiased=unbiased, demean=True)
    return cvf / (np.std(x) * np.std(y)) 

# 需要导入模块: import numpy [as 别名]
# 或者: from numpy import correlate [as 别名]
def norm_corr(x,y,mode = 'valid'):
    """Returns the correlation between two ndarrays, by calling np.correlate in
'same' mode and normalizing the result by the std of the arrays and by
their lengths. This results in a correlation = 1 for an auto-correlation"""

    return ( np.correlate(x,y,mode) /
             (np.std(x)*np.std(y)*(x.shape[-1])) )



# from matplotlib axes.py
# note: self is axis