def is_ignored_roi(roi, ignore_data):
    """Determine whether a specific ROI should be ignored

    Parameters
    ----------
    roi: drymass.roi.ROI
        ROI instance
    ignore_data: list of str
        List of strings of the form "image_index" or
        "image_index.roi_index" that identify ROIs that
        should be ignored. For instance
        ["1.0", "2.1", "3"].
    """
    imid = roi.image_index
    roid = roi.roi_index
    if ignore_data and (str(imid) in ignore_data or '{}.{}'.format(imid,
        roid) in ignore_data):
        return True
    else:
        return False
