Python scipy.special.cbrt() Examples

The following are 10 code examples of scipy.special.cbrt(). You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. You may also want to check out all available functions/classes of the module scipy.special , or try the search function .
Example #1
Source File: scipy_special.py    From Carnets with BSD 3-Clause "New" or "Revised" License 6 votes vote down vote up 
def get_scipy_special_helpers():
    import scipy.special as sps
    SCIPY_HELPERS = {}
    for name in dimensionless_to_dimensionless_sps_ufuncs:
        # TODO: Revert https://github.com/astropy/astropy/pull/7219 when
        #       astropy requires scipy>=0.18, and loggamma is guaranteed
        #       to exist.
        # See https://github.com/astropy/astropy/issues/7159
        ufunc = getattr(sps, name, None)
        if ufunc:
            SCIPY_HELPERS[ufunc] = helper_dimensionless_to_dimensionless

    for ufunc in degree_to_dimensionless_sps_ufuncs:
        SCIPY_HELPERS[getattr(sps, ufunc)] = helper_degree_to_dimensionless

    for ufunc in two_arg_dimensionless_sps_ufuncs:
        SCIPY_HELPERS[getattr(sps, ufunc)] = helper_two_arg_dimensionless

    # ufuncs handled as special cases
    SCIPY_HELPERS[sps.cbrt] = helper_cbrt
    SCIPY_HELPERS[sps.radian] = helper_degree_minute_second_to_radian
    return SCIPY_HELPERS
Example #2
Source File: test_basic.py    From Computable with MIT License 5 votes vote down vote up 
def test_cbrt(self):
        assert_approx_equal(cephes.cbrt(1),1.0)
Example #3
Source File: test_basic.py    From Computable with MIT License 5 votes vote down vote up 
def test_cbrt(self):
        cb = special.cbrt(27)
        cbrl = 27**(1.0/3.0)
        assert_approx_equal(cb,cbrl)
Example #4
Source File: test_basic.py    From Computable with MIT License 5 votes vote down vote up 
def test_cbrtmore(self):
        cb1 = special.cbrt(27.9)
        cbrl1 = 27.9**(1.0/3.0)
        assert_almost_equal(cb1,cbrl1,8)
Example #5
Source File: test_basic.py    From GraphicDesignPatternByPython with MIT License 5 votes vote down vote up 
def test_cbrt(self):
        assert_approx_equal(cephes.cbrt(1),1.0)
Example #6
Source File: test_basic.py    From GraphicDesignPatternByPython with MIT License 5 votes vote down vote up 
def test_cbrt(self):
        cb = special.cbrt(27)
        cbrl = 27**(1.0/3.0)
        assert_approx_equal(cb,cbrl)
Example #7
Source File: test_basic.py    From GraphicDesignPatternByPython with MIT License 5 votes vote down vote up 
def test_cbrtmore(self):
        cb1 = special.cbrt(27.9)
        cbrl1 = 27.9**(1.0/3.0)
        assert_almost_equal(cb1,cbrl1,8)
Example #8
Source File: figtools.py    From pycog with MIT License 5 votes vote down vote up 
def scott(data, ddof=0):
        """
        Scott's rule for the number of bins in a histogram.

        """
        if np.std(data, ddof=ddof) == 0:
            return sturges_rule(data)

        h = 3.5*np.std(data, ddof=ddof)/cbrt(len(data))
        return int((np.max(data) - np.min(data))/h)
Example #9
Source File: test_quantity_ufuncs.py    From Carnets with BSD 3-Clause "New" or "Revised" License 5 votes vote down vote up 
def test_cbrt_array(self, function):
        # Calculate cbrt on both sides since on Windows the cube root of 64
        # does not exactly equal 4.  See 4388.
        values = np.array([1., 8., 64.])
        assert np.all(function(values * u.m**3) ==
                      function(values) * u.m)
Example #10
Source File: camera.py    From camera.py with MIT License 4 votes vote down vote up 
def _distort_tsai(self, metric_image_coord):
        """
        Distort centered metric image coordinates following Tsai model.

        See: Devernay, Frederic, and Olivier Faugeras. "Straight lines have to be straight."
        Machine vision and applications 13.1 (2001): 14-24. Section 2.1.
        (only for illustration, the formulas didn't work for me)

        http://www.cvg.rdg.ac.uk/PETS2009/sample.zip :CameraModel.cpp:CameraModel::undistortedToDistortedSensorCoord

        Analytical inverse of the undistort_tsai() function.

        :param metric_image_coord: centered metric image coordinates
            (metric image coordinate = image_xy * f / z)
        :type metric_image_coord: numpy.ndarray, shape=(2, n)
        :return: distorted centered metric image coordinates
        :rtype: numpy.ndarray, shape=(2, n)
        """
        assert metric_image_coord.shape[0] == 2
        x = metric_image_coord[0, :]  # vector
        y = metric_image_coord[1, :]  # vector
        r_u = np.sqrt(x ** 2 + y ** 2)  # vector
        c = 1.0 / self.tsai_kappa  # scalar
        d = -c * r_u  # vector

        # solve polynomial of 3rd degree for r_distorted using Cardan method:
        # https://proofwiki.org/wiki/Cardano%27s_Formula
        # r_distorted ** 3 + c * r_distorted + d = 0
        q = c / 3.  # scalar
        r = -d / 2.  # vector
        delta = q ** 3 + r ** 2  # polynomial discriminant, vector

        positive_mask = delta >= 0
        r_distorted = np.zeros((metric_image_coord.shape[1]))

        # discriminant > 0
        s = cbrt(r[positive_mask] + np.sqrt(delta[positive_mask]))
        t = cbrt(r[positive_mask] - np.sqrt(delta[positive_mask]))
        r_distorted[positive_mask] = s + t

        # discriminant < 0
        delta_sqrt = np.sqrt(-delta[~positive_mask])
        s = cbrt(np.sqrt(r[~positive_mask] ** 2 + delta_sqrt ** 2))
        # s = cbrt(np.sqrt(r[~positive_mask] ** 2 + (-delta[~positive_mask]) ** 2))
        t = 1. / 3 * np.arctan2(delta_sqrt, r[~positive_mask])
        r_distorted[~positive_mask] = -s * np.cos(t) + s * np.sqrt(3) * np.sin(t)

        return metric_image_coord * r_distorted / r_u