Convert axes labels to experiment duration in hours/minutes

    Notes
    -----
    Matplotlib FuncFormatter function
    https://matplotlib.org/examples/pylab_examples/custom_ticker1.html

def nsamples_to_hourmin(x, pos):
    '''Convert axes labels to experiment duration in hours/minutes

    Notes
    -----
    Matplotlib FuncFormatter function
    https://matplotlib.org/examples/pylab_examples/custom_ticker1.html
    '''

    h, m, s = hourminsec(x/16.0)
    return '{:.0f}h {:2.0f}′'.format(h, m+round(s))