def GetColumn(data, index):
    """Extracts the given column from the dataset.

    data: sequence of rows
    index: which column

    Returns: map from int year to float datum
    """
    res = {}
    for row in data:
        try:
            year = int(row[0])
            res[year] = float(row[index]) / 10.0
        except ValueError:
            pass
    return res