Custom power ticker function.

def power_tick(val, pos, times_sign=r'\times'):
    """Custom power ticker function. """
    if val == 0:
        return r'$\mathregular{0}$'
    elif val < 0:
        exponent = int(np.log10(-val))
    else:
        exponent = int(np.log10(val))
    coeff = val / 10**exponent

    return r'$\mathregular{{{:.1f} {} 10^{:2d}}}$'.format(coeff,
                                                          times_sign,
                                                          exponent)