def extract_delta_time(data):
    '''
    Creates array of delta times between points in seconds
    '''
    times, coordinates = data[:, 0], data[:, 1:]
    return np.array([delta_float_time(times[i], times[i+1])
                     for i in range(len(times)-1)])
def test_delta_time():
    datestr_array = [
        '04-08-2015_14-35-50_PDT',
        '04-08-2015_14-52-31_PDT',
        '04-08-2015_14-52-37_PDT',
        '04-08-2015_14-59-30_PDT',
        '04-08-2015_14-59-30_PDT',
        '05-08-2015_15-46-30_PDT',
        '05-09-2015_15-46-38_PDT',
    ]
    
    dates_nums = [date_str_to_num_converter(el) for el in datestr_array]
    
    dts = []
    for i in range(len(dates_nums) - 1):
        dts.append(delta_float_time(dates_nums[i], dates_nums[i+1]))

    expected_dts = [1001, 6, 413, 0, 89220, 2678408]
    assert(expected_dts == dts)