Returns polar mesh for matplotlib.pyplot.pcolormesh() in polar coordinates.

    polar coordinates of data points -> polar mesh for colormesh
    polar coordinates is assumed to be equidistanced in a sense that
    the r_values and theta_values are assumed to be equally-spaced.

def augment_polar_mesh_for_colormesh(r_values, theta_values):
    """
    Returns polar mesh for matplotlib.pyplot.pcolormesh() in polar coordinates.

    polar coordinates of data points -> polar mesh for colormesh
    polar coordinates is assumed to be equidistanced in a sense that
    the r_values and theta_values are assumed to be equally-spaced.
    """

    N_r = len(r_values)
    N_theta = len(theta_values)

    delta_r = (r_values[-1] - r_values[0]) / (N_r - 1)
    delta_theta = (theta_values[-1] - theta_values[0]) / (N_theta - 1)

    mesh_r_values = (np.arange(N_r + 1) - 0.5) * delta_r
    mesh_r_values[0] = 0
    mesh_theta_values = (np.arange(N_theta + 1) - 0.5) * delta_theta

    mesh_R, mesh_Theta = np.meshgrid(mesh_r_values, mesh_theta_values, indexing='ij')

    return mesh_R, mesh_Theta