def slice_clusters(cluster_data, z, dz):
    """
    Returns all clusters from cluster_data between redshifts z-dz and z+dz

    Parameters:
    ------------
    cluster_data : `numpy.ndarray`
        Input cluster catalogue

    z : `float`
        Input redshift, the center of the redshift bin

    dz : `float`
        Input redshift increment/decrement

    Returns:
    ------------
    clusters : `numpy.ndarray`
        All clusters within z-dz and z+dz
    """
    clusters = cluster_data[(cluster_data['z_lambda'] >= (z - (dz / 2.)))
                            & (cluster_data['z_lambda'] <= (z + (dz / 2.)))]
    
    return clusters