get_angle

import numpy as np
from numpy import linalg as la

def get_angle(centerpt, refpt, measurept):
    '''
    Function to get any angle you want.

    Args:
        centerpt (:class:`numpy.ndarray`) : nx2 array, position of center point
            of your choice, i.e. midpoint of ears, back of head.
        refpt (:class:`numpy.ndarray`) : nx2 array, position of reference point
            of your choice, i.e. the nose in this case.
        measurept (:class:`numpy.ndarray`) : nx2 array, position of the cricket.

    Returns:
        angle (:class:`numpy.ndarray`): nx1 array of angles across time
    '''

    #match lenght of arbitrary points chosen for ref or center point
    maxmeasure=np.max()

    #calculate the normalized vectors for getting the angle
    #possibly get all of this into a df
    n1=(measurept-centerpt)/la.norm((measurept-centerpt))
    n2=(refpt-centerpt)/la.norm((refpt-centerpt))

    #use arctan to get the angle at every point in time
    angle=np.empty([maxmeasure,1], dtype=float)
    counter=0
    for i in range(0,maxmeasure):
        angle[i,:] = np.arctan2(la.norm(la.det((n2[i,:], n1[i,:]))), np.dot(n1[i,:], n2[i,:]))
        counter +=1
    #determine if angle is to the right or left

    return angle