def get_time_points(data, ds):
	"""
    extracts time points / x values in a given PTCF

    :param data: ptcf data frane
	:param ds: data set for which the different time points should be determined
    :return: list of time points
    """ 
	return len([x for x in list(data) if x.startswith(ds) & (x!="ds1_cluster") & (x!="ds2_cluster") & (x!="gene") & (x!="ds1_median") & (x!="ds2_median")])