yablog: calculate cosine with python numpy

calculate cosine with python numpy
purpose

Calculate "cosine" determined by pair of vectors using python and its package named numpy. Firstly I show you the definition of cosine in linear space, and Secondly I share sample python code for calculating cosine.

definition of cosine in linear space

$\vec{a} = (a_1, a_2, \cdots, a_n)$
$\vec{b} = (b_1, b_2, \cdots, b_n)$
$\cos \theta = \frac{\vec{a}\cdot\vec{b}}{||a||||b||}$

python code for calculating cosine

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import numpy

def get_cosine(v1, v2):
    """ calculate cosine and returns cosine """
    n1 = get_norm_of_vector(v1)
    n2 = get_norm_of_vector(v2)
    ip = get_inner_product(v1, v2)
    return ip / (n1 * n2)

def get_inner_product(v1, v2):
    """ calculate inner product """
    return numpy.dot(v1, v2)

def get_norm_of_vector(v):
    """ calculate norm of vector """
    return numpy.linalg.norm(v)

def get_radian_from_cosine(cos):
    return numpy.arccos(cos)

def get_degrees_from_radian(cos):
    return numpy.degrees(cos)

def main():
    v1 = numpy.array([1, 0])
    v2 = numpy.array([1, numpy.sqrt(3)])
    cosine = get_cosine(v1, v2)
    radian = get_radian_from_cosine(cosine)
    print get_degrees_from_radian(radian)

if __name__ == "__main__":
    main()